Ok, here goes, I've tried all three effects and I own a Korg AX3000G, if you're looking for the best value around it's of course going to be the AX3000G, the GT8 while slightly more expensive has the versatility and it's a good metal sounding effect, if you're into Blues and 70's rock you wanna go for the AX, the thing is though, while I praise the AX, the AX doesn't have the versatility of the GT8, being newer than the AX, the GT8 gives u a lot more options, but if you've got the cash, I saw someone selling a Digitech GNX4 on Jamtank for around RM1500, and I think that would be your best bet, while I haven't tried this unit personally, from the reviews it seems like a great unit. The GNX4 comes with a built in XLR input and you can record directly into the GNX via it's 8 track recorder but the drawback it's stored in Compact Flash form. The Pod XTlive one the other hand, has great tone, and if you want to go for something that got great tone, you wanna go for the Line 6 products, their tones are unbeatable. Even their early editions like the POD and the POD 2.0 sound awesome. But at the end of the day you're running top notch effects with a really crappy sound you're gonna get really crappy sounds. So my advice is, invest in a good amp, a good guitar with decent sounding p/ups and then go for the multieffects. Just my 2cents.

Cheers;
Chris.