Re: RG1570z vs RG2550z and why?
If you like 2550, you can't go wrong with 1570. I own two MIJ 550s, 570 and a Prestige 2550. Basically, the 550s became 2550s and 570s 1570s. They are basically the same guitars with the main difference being in pickguard. I remember when I fisrt got a 570 I really missed the pickguard so I just ordered one form evilbay and drilled the holes. You can't tell the difference now.
My advice, get the 1570. Great guitar, cooler inlays, cheaper and just as good as 2550.
PS I'm not sure about the pickups though... Maybe 1570s use the Ibanez V pickups which are inferior to the IBZ/DiMarzios used in 2550. But anyway, you'll probably be changing the pickups after a while. May I suggest Breed (neck) and Evo2 in bridge?