Interesting article in the most recent Bicycling magazine by none other the Jens Voigt: despite all the advancements in technology over the last two decades, only two riders in the most recent Paris-Nice TT beat Sean Kelly's time over the same course 20 years ago. Voigt's conclusion: the bike basically doesn't matter, the engine makes the difference. The differences between the S3 and the S5 most likely do not translate to differences in a road race with the intrinsic effects of being in the pack and tactics etc. Keep working hard and buy whatever bike takes your fancy (depending on trial rides and fitting).
2006 Lynskey Level 4 Road, Zipp 303 with PT, Ultegra Di2
2012 Cervelo S2, Zipp 404 with PT, Ultegra
2012 Ritchey Breakaway, 105
Colnago Master, Ambrosio Nemesis, DuraAce
2010 Stevens Team Ultegra Cyclocross
2006 Raleigh Rush Hour
2001 Giant XTC NRS1