What 3G bands does Argentina or your current carrier use?
(choices being 850/900/1700/1900/2100)
Did you give him the wrong link? All the phones here have worse screens and CPUs than the nexus one, only one has a WVGA screen and the rest are HVGA/QVGA.
I think you should be able to get a Nexus S at or below $200 if you look carefully, but just be aware of a few things. i9020i is the European variant with 900/1700/2100 bands, i9020a is the American variant with 850/1900/2100 bands and there is another variant that has SLCD rather than the AMOLED screen. I would recommend going for the AMOLED even with pentile because voodoo apps can tweak the colors to proper levels.
I'll poke around for a dual core phone in that price range later, but if you had to get a single core phone, the nexus S is a little better than the nexus one, only real disadvantage being the nonexpabdable storage.