Just sold my Profile Design Century clip-ons on
ebay yesterday - sorry!
I started with these but after 3 races I've already upgraded to Profile T2+.
Depends on your budget. The century clip-ons are OK to try-out aero bars and see if you like them (they cost £40-£50 depending on where you buy them) but if you get on well with aero bars you'll probably want to sell them on and upgrade pretty quickly. The Profile T2+ costs £100 and is still labelled as 'affordable' - you can pay silly money for clip-ons!
You'll almost certainly need a TT/Tri specific saddle if you fit aero bars, as normal saddles are very uncomfortable when using aero bars.