repost randall RB-125-115 plus new amp questions

okay, since this sat in the live sound forum for about a month..i figured to repost in a better forum i guess..anyways

http://www.ampeg.com/products/classic/svt450h/index.html

this forum needs a drool smiley..

anyways. the issue here is matching cabinets to this head. ive heard great things about mosfet powered bass amps/ampeg amps in general. and since this one is such great quality with it being affordable as well (something you dont see very often in the guitar market regarding brand names) i am thinking about saving up for it, provided they keep it in production.

i wont discuss here tubes vs. solid state, as thats what im concerned about here. so down to business.

http://www.ampeg.com/products/b/b115e/index.html
http://www.ampeg.com/products/b/b410he/index.html

these are the two cabinets (i want to purchase both) that i am interested in rigging up to the head. my issue here is ignorance on the subject. every article ive read online about this topic leaves me dumbfounded and confused afterwards. i am not an electrician and ohms/wattage relationship i understand the basics of...when talking about 1 amplifier. but when combing heads with cabinets, i am about as smart as forrest gump in a smart guy convention.. i have objectives here that i wish to accomplish with a new bass rig setup.

-i want a bass rig that is of high quality, and can hold its own in a club/restaruant/high school basketball court sized area.
-i want the cabs matched to the heads so it does not catch fire from an improper set up (too many watts for the head to produce for the cabs, producing power amp distortion/clipping from the amp producing more watts than it is rated for, then overheating as a result)
-on the other hand i want the rig to be performing up to its potential, i dont want to put too few watts into a cab.. like trying to put a practice amp's head and hooking it up to a marshall 4X12 double stack, it just wont work.

i notice that the ohms situation between the cabs and head ive chosen will work. the head will produce 450 watts at 4 ohms. both cabs are 8 ohms, combine the two and the result is a 4 ohms resistance. i am just not sure what relationship the wattage between the two cabs and the head should be. should the added cabinet wattage rating RMS be greater than the head when combined together? or should it be less? EX. my heads rating here is 450 watts @ 4 ohms/combined cabs wattage RMS is 400 watts at 4 ohms. is this a safe rig? or should i have the combined wattage of the cabs be slightly greater than the heads output? say for instance ive i were to add a small 2X10 or 2X12 cab to the stack? (COMPLETELY disregarding the resulting resistance for that last part)

i also have an old bass amp, a randall RB-125-115 made in 87' with an eminence 15" speaker in it in place of the original jaguar high excursion speaker. the sound it makes is quite frankly, fantastic. it has a 5-band EQ, and using that i can pull massive detail out of my bass guitar and hone in on the tone i want. i am currently using this as my small gig amp and i love it! i wish randall still made higher power bass amps! anyways.. this amp produces 120 watts at 4 ohms when both speaker outs on the head are used (head to speaker cab output). but the speaker in the combo itself, is the only one being fed power from the head as there is no cab that i have to be powered by the other signal out, so the head is running at whatever watts @ 8 ohms, not utilizing the full power of the head, i think.. now, this amp has been out of production for years and years so manuals and specifications on the amp itself are scarce at best. so as a result, i am not sure of any of its specs, or if it is capable of producing 120 watts at 8 ohms or not. i know some amps will produce the same wattage no matter what the resistance is in ohms (350 watts at 4 or 8 ohms), just because of the way the circuits are set up... randall does this with a lot of their solid state amps, but as this one is old, im not positive if that is the case. if the 120 watts the head is capable of producing are not being used while running under 8 ohms, then i would like to get a cabinet to utilize the full power of the head. but seeing as their arent many cabs made nowadays in that power range anymore.. any suggestions on a good solution? does anyone know anything about this amp and maybe where i could find a manual/specifications sheet for it? i may be willing to get one made too..

another question about the same amp.. the power switch has 3 positions, up=on, middle=off, down=on. im curious as to why they made it this way? ive noticed that the problem of non-grounded strings on my bass isnt as pronounced in the down position. but in the up position after about 2 minutes of playing, if you dont touch anything metal on the guitar, you hear a buzzing, which goes away when you touch something metal. does putting it in the up position engage a different tone circut? ive noticed there is a very slight change in tone between the two positions, but my ears may be playing tricks on me.. this amp has been used in countless small gigs by the previous owner, and the love is quite apparent on the tolex.. i can provide pictures of the head and the circutry if necessary, as the head is held in by only 4 screws and is quite easy to work on.. there are also two inputs, one says "HI 6 dB" the other says "LO 0 dB" any explanations on the difference between the two? maybe one input for active basses and one for passive?

if you have no idea what im asking i will try to clarify for you a bit better.. sorry for the lump of reading!

PS: im actually looking at the SVT-CL, not the SVT-450.. 300 watts, all tube.

Derek.