I picked up a used DC 4-2-1 and love it. It does get hotter under the hood than before (since there's no longer a heatshield), but it gives good gains. I'm seriously considering going with a mild and cheap turbo now because I hate the thin air at this altitude (5820ft), but I can always just sell the header when the turbo goes in.

So, I would suggest finding a good deal on a used header and then you can just sell it when you get a turbo. You'd probably be able to sell it for close to what you payed for it too, assuming it stays in good condition.