I don't start seriously considering adding a console to my collection without a minimum of 3 must-have titles (or six I'm very interested in.) At that point, I figure out the 'real cost'- becuase it's never just the system, it's the system and a game and maybe an extra controller/memory unit/standard accessory almost everything uses (I'm looking at you, nunchuk!). From there I figure out how affordable the system is for me, and if I should start saving or hunting for sales or just waiting on a price drop.
If the rumors about the new Xbox being anti-used end up true, I won't buy one at all. I LIKE my old systems. I still have an 8 bit Nintendo hooked up to my TV. They're aren't excactly piles of new games around for NES. Why invest in a system that's basically got a 'set shelf life'- oh, new games are out, you can't add to your collection anymore. It sounds awful, I hope it doesn't pan out.