I would say get the one that fits.
After that, I'd say go for the P3, and maybe some Flos, or used 404's. You'll still have spent less money than the felt, and you'll be on a pretty darn fast ride.

Are you comparing the DA3 because that is what your LBS has in stock? It seems like the DA4 might be a closer comparison with the P3.

Off the top of my head geometry between the two is similar. Your best bet is probably the cervelo and buy a set of flo's. The upside to this is you can have a set of dedicated training wheels/tires.

Edit: don't forget an omega front brake ;)

Local shop has the DA3 and it has the upgraded wheels and components that still meets my budget. To get a P3 with Dura Ace would be roughly $5,300 and it wouldn't have the upgraded wheels. If Cervelo had something in between that was compatible with the DA3 then I would have included it. I am also very familiar with Felt, I've had 2 (but neither a tri bike) but I really like to lines on the Cervelo. Ideally, the local shop has a 2013 P5 Three Red for $5,100, if it was just a little lower I would be looking at that but as I was saying $4,500 is really my peak. I'm just concerned because the Felt does not look that fast (in comparison) and I can't really find any reviews on the 2014 DA3.

If I remember correctly the Kristin Armstrong won the gold at the London Olympics TT on a DA... So it is plenty fast.

Also the fit on the two bikes is very different. The felt is long and low vs the 2014 P3 which has a similar fit to the new generation of tri bikes shorter reach, higher stack.