I think you just price in the age and accept the better deal. That bike was never a top shelf superbike, so keep that in mind when negotiating.
A good value are 1st generation Speed Concepts, Cervelo P2's.
Honestly a lot of it is about fit. I just jumped from a 1st generation 7 series Speed Concept to a 9 series and I'm waiting on a lower stem to come in. But sitting 3cm higher, I'm not faster, if not slower than I was on my previous bike. Point being the the bike fit means a lot more than the bike itself.
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