You all seem like a handsome collection of guitar-goers who can help me!

My amp is not very good, its a Line 6 spider IV 15 watt. i may not be very good either, but im progressing and beginning to jam with people, and feel a better amp will be necessary pretty soon.

Gear: I'm using an Ibanez RG321 mh with seymour duncan distortion pups, its not the bee's knees per se` but it sounds nice, especially on friend's amps so i feel an amp upgrade would be more efficient than a guitar upgrade. As far as pedals, i use a Zoom G2.1Nu effects/USB/expression pedal

Sound preference and budget: budget will be up to about $300-400, possibly more depending on if there are ridiculous upgrades for a slightly higher budget. I've been working on some Dream theater, Iron maiden, Rainbow, Steve Vai, Tenacious D, Pink Floyd.. these kinds of things.

I've been checking out some reviews here and talking with friends, but there's a lot of info to take in. i ultimately want a Mesa/Boogie but i dont gots the cash like that, so Ampeg, Vox, Peavey, Blackheart all look good, but im hoping some of you can point me in the right direction? thank you lots!