Looking for some advice on a new practise amp

Hi everyone.

I've been playing guitar for about half a year now and am considering buying a new amp. I'm not that clued up on amps and whats best for what, I play mostly metal & Rock, bands along the lines of Rage against the Machine, Rise against, Ozzy, AC/DC.

I Already own a Digitech RP355 Multi-effect processor, so I'd like to avoid amps where i'm going to be spending unnecessarily on stuff like this and invest purely on sound quality.

I'm looking to spend in the area of £150 ($234.64)

NB: My current guitar is a Ibanez GRG170DX ( http://www.ibanez.co.jp/world/country/frame_uk.html )

Thanks in advance for your help