Get something to connect your guitar to your computer with any kind of external USB sound input (such as a 'guitar link', 'stealth plug' or an 'InPort', any of those would do the trick, you can find stuff like that on trademe no problem
). Then use software like Guitar Pro or Fruity Loops (the latter will require custom sound packs) and baam, you can produce literally ANY guitar tone you could possibly imagine. You'll probably need decent computer speakers though, although you can get multipurpose amps that can link up to your computer as well as plug the guitar in directly.
Sorry as I realise this doesn't answer your question exactly, but it's an alternative to buying an expensive amp that only has a few tones and effects. A big amp with a decent soundbank can be great for performance purposes but if you just want to mess around in your room, you'll be able to mess around with a LOT more if you use a computer. I started off with a 60w amp and eventually got a 100w, which was great, and loud, but kinda limited with it's presets until I realised I could use it as an output from my computer and a whole new world opened up. You can actually find sound packs of Dream Theater guitar tones and presets on the internet to import to guitar pro or whatever software you're using. I don't have anything to recommend but most modern 60w amps would do the trick (new ones are a lot better than they were 10 years ago although make sure to check their frequency input because if it's designed only for guitars then it's not a good idea to plug your pc into it just in case you output sounds that are too low or high for your amp. Anyone who's plugged a guitar into a bass amp for example, will tell you that it doesn't end well). Or, consider upgrading your pc speakers, it's worth it.
Honestly, this method can be just as effective as a fancy expensive amp and will probably be a lot cheaper.