GLX's are a bit overpriced...and most of the effects are pretty useless.I know the lights are cool and all,but you could get such better amp for that price.FYI 120Watts is plenty for gigging.You would need 1000Watts to be able to tell any difference from 100watts.Instead of paying for more Watts and onboard effects your probly not going to use,I suggest more speakers.If you have 300watts running through a 1x12 cab,and 50watts through a 4x12..which one will push more air(resulting in "loudness")?Simply put,more speakers means more air pushed.
Go to avatarspeakers.com and take a look at the 4x12 cabs.
If you dont like those(for some unknown reason)then check out the Behringer 4x12 cabs.I say those simply because there the best for the price..you can get any cab you want.Then get the amp head of your choice...randall rh100,carvin sx200 or 300 and stuff like that.Remember I'm keeping in mind your spending power.I own a Carvin sx200 halfstack and it kills...$650 brand new from carvin.A 2x12 combo isnt bad at all,but for around the same price(give or take $50)you can get the versatility of a stack.You could add another cab in the future if wanted too.

All in all...A 120Watt 2x12 combo will cut it(take a look at the randall rg100 or 200 2x12 combos).If you can live without the glowing red lights and pretty much useless effects(and the often poor sound from crates)then you can save some money and get a great amp.I really urge you to consider a stack though,since it will equip you for much larger louder outdoor gigs where your sound escapes.

I have no idea what amps cob or blind guardian use...sorry.

Later! \m/