I'm not familiar with the SZ320, but I'm very familiar with Epiphone. Find one that feels good and has a serial number starting with EE - this denotes it came from the new Epiphone Electric factory in China. They seem to be pumping out better products than what Ibanez offers from Korea (non-Prestige) or Indonesia.
It's worth it to pay the extra for the Standard over the Studio, but don't bother with the Standard Plus Top. Those fancy looking flamed and
quilted maple tops are very thin veneers and do nothing to alter the sound. They don't have genuine, thick maple caps like Gibson.
Eventually, swap out the pickups, pots, and caps and you'll have yourself a fine guitar for the money.