I've heard some great things about the Sargent seat, however I confess to having the Corbin seat. On long-day two-ups, it's pretty common for my pillion to fall asleep, the seat is that comfortable.
http://www.triumphnet.com/st/acc/corbin/
It's light-years different than the stock seat, which absolutely stinks, IMHO. The Corbin is flat, can be described as "hard" by some (not me), but all that depends on your arse. The flat/hard combo suits my 6'2" 220lb frame fine and gives me lots of room to move laterally on the twisties... It's now to the point where I just leave it on full time...so much for the stock seat and cowl.
Either way, ditch the stock seat. Your prostate will thank you a year or two down the line.