GNX3

I currently have a Fender Frontman amp, which is fine for clean sound, but not good at all for any kind of distortion or effects. I've been trying to decide what to upgrade to and can't decide which route to take. First I thought about an amp like the Roland Cube 30 or 60 that has good effects, then I considered the Digitech RP100a and just use that with my current amp. I also looked at the Digitech GNX3. Since I'm not a performer, I was wondering if the GNX3 would be better than just buying a new amp, and I could just use that with speakers for all the effects I wanted, and would still have something that I wouldn't outgrow. Would that make more sense than buying another small amp with a few effects built in?