Im gonna be a senior next year and i recommend doing what i did. Take the SATs in OCT/NOV. Yeah you wont have your PSAT scores and in fact you'll be taking the SAT before the PSAT. However this way you can take the SAT right after your summer of studying. In addition, in May you will be working on AP testing and that time is better reserved for SAT IIs (for example i took SAT2 US history the day after the APUSH test). Then come June i got an early case of senioritis
so i personally wouldnt recommend taking the SAT then. Taking it early in the year and getting it over with is like taking a huge rock of your back for the rest of the year. That way you dont have to worry about it and instead worry about your grades throughout the year.
My SAT scores in OCT 05 = 2180
My PSAT scores in OCT 05 = 212 (5 more pts for semifinalist in Cali :| )
OH and BTW the curves are predetermined so taking it when Seniors are taking it will not affect your scores.