I think I can trade in my 2007 Dual with ultegra for a 2008 P2C ultegra if I spend about 500 extra cash. Is this worth it or should I just get racing wheels?
500 bucks seems like nothing for a new P2C.
Get the bike now, and race wheels some other time.
It depends on you, your riding, and your fit(s)
If you have just one bike and will stay with one bike, then the Dual is probably good. If you already have a road bike, then the P2C is probably the right choice. This assumes that both bikes can be fitted to you properly for the riding you do.
That said, I think the P2C is probably the best tri bike out there, for the vast majority of people (P3C/P4 are nice, but arguably too much bike for most people) and to get on one for just $5 hundy more seems like a sweet deal to me.
I currently have a 650C P2K and love it. Upgrading to the P2C (now just the P2?) is a dream I have, but doubt will come true.
good luck and enjoy whichever bike you settle on. With a Cervelo, you can’t go wrong
are you confused? the Dual and P2C have identical geometry. If one fits the other definitely will.
I think he thinks the dual a dual use bike (which is actually the soloist)
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I must be confused. I thought the Dual had a slacker seat tube angle than the P2, to be half way between a road geometry (ie Soloist) and a tri geometry (P2 (now P1). Hence the name Dual…as in could be set up for road or tri. Sorry for my confusion. Thanks for the heads up.
All the way to lunchtime for me to learn something new today.I guess I can go home early now 
Get the bike. Your Dual is probably worth $1000, so you are essentially paying $1500 for a P2C - that’s a great deal!
500$ sounds like a very fair price for Dual->new P2C upgrade. Carbon frame is worth it, imho.
If it’s speed you’re looking for, upgrading from a Dual to a P2C will not make you faster.
do it. I just switched from a QR tequilo to a P2C and the ride is night and day. Granted the Dual “might” be a nicer bike than the Tequilo…but if it is, they are at least in the same ballpark. The P2C is a big jump up…honestly, I was surprised by how much better it rides. it is smoother and the difference in power transfer is dramatic.