Pretty much all the TRI guys I know (and oddly enough, I know too many) have moved from TT bikes to aero bikes with Tri bars in the last couple of years. Watching them migrate really stopped my from buying a TT bike for myself. The standard complaints.... they ride hard and handle poorly. I've experimented with clip on bars on an endurance style bike and as much as I could see the gains from the bars, the weight of the bars really, REALLY affected the handling of the bike in a bad way... turned it into a whale.
So... I'd suggest that you start with some reasonably cheap clip ons (obviously with your setup, you're changing the handle bars) and go from there. If the handling still works for you,stick to them for a bit and then decide if you're willing to buy a nicely used TT bike (I'm with you on disks... but one think I really thing a TT bike needs is electronic shifting... having to move hand positions from brakes to down shift seems very dangerous/inconvenient to me).