FrancoisO In my humble opinion: The single item which makes the most difference - wheels! Deep section wheels normally start making a difference once you move 33km/h or faster. A disk wheel is probably the fastest way to go (and also starts at 33km/h or so). But any wheelset with good rolling resistance should be the most positive addition to your bike. TT bars assists mainly (for us Joe Schmo's) in attaining a better aero position. this also makes a large difference, but keep in mind that you need to ride in that (uncomfy) position most of the time. TT frame mainly looks cool! - you can achieve the same geometrical advantages of a TT frame on a normal road frame by getting a "bent" seat post. TT helmet - if you are strong, maintain your position and really racing for time, then an aero helmet would make a difference. I have done quite a bit of research with regards to TT, among other a masters degree research paper done at an American Univarsity, and the findings come down to the fact that: real time benefits with regards to aerodynamics and gear are mainly dependant on the wheels you use and the position you are riding in. Also that there is a logarithmic balance between a very aero ,uncomfortable position, and a comfortable (max power) position. Other gear and positioning (helmet, gloves/no gloves, bottle position, arms position, etc) factors only makes a difference of few seconds over 40km and maybe a minute or two over 180km - IF YOU MAINTAIN A TRUE TT POSITION. Thus standing up (or even sitting up) will already negate the smaller aero factors. All said, I recommend getting clip on TT bars for aero position benefit, and good wheels for most effective time benefit. 50mm deep section wheels are great as they can also be used on road races. Disk and deep sections over 50mm are TT specific and mainly more expensive, and are only recommended if you are going full trim on TT. (when I put 50mm wheels on I immediately gained 20min on 100km - and I actually bought a disk today seeing as I LOVE TT, and its cool to pimp a disk... along with my mullet...) the alternative is just to train more effectively >>>
