I currently have a Sora 3 x 8 sp STI group on my road bike that is going to be transfered to a modern frame - however, my LBS has an Ultegra front/rear derailluer set that I can pick up for $90. Is it worth buying the derailluers only and upgrading shifters at a later time, or should I wait and upgrade all at once? They have a set of Ultegra shifters as well, but they are triple, and I want to move to a double up front, so my plan is to wait until I am ready and get the rest of the drivetrain when I am ready for that.

I have my decals and am taking everything off of the frame this weekend, then off to the powdercoater.

No way. $90 is way to much for something that will shift marginaly better than 105. My advice is to save some money and buy some good 105 derialleurs out of the for sale/wtb sub forum or grab some NOS ones off of ebay.

I did something very similar and I wouldn't recommend it for your situation. The 8 speed chain is a little wide for the Ultegra derailleurs and it rubs on the jockey cage at the rear and needs lots of trimming at the front.

You can put on a nine or ten speed chain but then you may have compatibility issues with your 8 speed cassette and front cranks. I did this because I was running a Campagnolo Super Record F/R derailleur and SIS shifting didn't work with those (cable pull/shift ratio is different to modern Shimano derailleurs).

Good enough - I'll wait until I can buy the whole set then.

Buy an entire bike, it may cost 2X what STI's and derailleurs will cost but you'll get an complete bike.

I figure I can do pretty well on ebay, without buying an entire bike. Maybe. I bought a full bike to get the STI's I have now, but I bought it on CL for $150, so I'm pretty much ahead. Maybe.

From Sora to Ultegra, I'd go when I had the whole group.

If 9-sp is your yen, Jim is right, you can get a complete 9-sp STI group for about double what you were going to spend on the Ultegra FD/RD. I just bought a complete Ultegra 9-sp group, front to rear, chain, cables, cassette, etc, $325.

If 8-sp is the deal, the 3x8 Sora's will work fine in double, you can adjust to noise-less trim on the FD. You can use 600 tricolor FD/RD and be shifting smoothly for $50 or so. 105 will work fine, but 8-sp 105 is hard to find.

As far as donor bikes, there were a lot of Cannondales put out with 105 STI stuff, you may be able to pick up an entire bike, STI-equipped, for $225-$275.

That's what I'm hoping. This isn't a priority, because what I have works, so I'm not too awful worried about it. I'll bide my time for now, unless I find a killer deal.

Hold out for Dura Ace. Trust me.

Sometime in the future I may just be insane enough to go with DA-7900 DT shifters, 10 Speed cassette and chain. For about $170 that will upgrade me from 8 - 10 speed. I'm figuring a few years riding with the 8 speed DT system and then I'll decide if brifters are worth it. I'd probably only settle for the Ultegra-6700 group if I go that way and then you have do it en-masse since there are numerous compatibility issues with brakes, chain sizes etc.

PS. From the research I've done incl. Sheldon Brown's site, a nine speed chain should work great with my setup (8 speed cassette, Ultegra SL derailleurs, vintage 53/44 crankset). I'll be trying it sometime this week or the weekend at the latest - HG-93 and PT Master Chain puller are poised and ready to go.