dollar for dollar, he's probably talking about a S14 or S15
BUT he lives in New Jersey, USA, so we don't get any of the cool features of the true silvia
You can get a S14 or S15 silvia for around . . . 8,000 for a nice one in good condition . . . but if you want it to perform on par with an s2000, you'll need to drop in a SR20DET engine and redo the suspension, modify the engine/turbo/etc.
all things considered, you'll pay a little more if you go with the S2000 initially, but it'll be a nicer car and it'll be street legal (engine swaps aren't legal if you use a jdm engine)
i'd take s2000 - and it'll be a 6spd versus 5spd for the 240