i know this has been answered before but the answers didnt have enough clarity for me. i was hoping some of y'all who have experience out there could help me choose between the two.

i can get the gt-6 for a good $150 less than the gt-8. however, it doesn't come with usb capability, and it doesnt have the dual COSM engines (so no dynamic mode).

what about sound quality though. is that roughly equivalent? anything else i should know? thanks for your help.
the GT-8 does not have USB either. Save your money and invest in the GT-8. You get more effects and preamp models in the 8 than you do the 6. The GT-6 isn't bad in terms of sound and effects quality, but you'll just get more for your extra $150 if you get the GT-8.
the gt-6 is awesome for effects, not amp models!

good flexability

gt-8 is good, maybe not worth 150 more

look on ebay

save yourself a bundle