Driver suggestions for DIY project

Just remeber that drivers are rather specific to the size of box used. You might want to pick up a book on loudspeaker building, it will give you the formulas and information needed to match the drivers to the cabinet. Not just any driver will do. You definaatly dont want to be shoving a driver that needs 5 cubic feet of space into a 1.5CFT enclosure.

I would probably go with either scan speak drivers or focal drivers. Ive been doing alot of research on loudspeaker construction, im hoping to eventually make a living out of it, and Focal and Scan Speaks seem like some good drivers.

but be sure you have matched the drivers to the box size or you will be hammering the square peg through the round hole.

I agree with elevick to at least consider Jordan. You can get Jordan or Tang-Band from creative sound
This site also lists DIY with Jordan drivers. I use Tang-Band W3-871S and it's very nice.

The Jordan drivers are not very sensitive (have listened to them twice in different enclosures).

I realize that some are running them with approx. 25 watt chip and tube amps, but I consider this to be about as low (in power) as I would go with the Jordans (not including low powered Wavelength, top of the line Audion or other amps of similar quality).

Based on a conversation I once had with Ronnie (the owner of Carolina Audio) 15 watts would not be enough power to do them justice and this is why I did not end up with Jordan (JX-92s) based speakers when they first became popular a few years ago.

I am also familiar with the Cary push/pull 2a3 amp and it has no more drive than the push/pull 6bq5 amp I was considering using with the Jordans @ the time.

Bennett -- the Hiquphon's a marvellous tweet and, on the drawing board, there is an endless line of mids that you could use (limited somewhat by the Hiquphon's medium sensitivity of 89-90db). (I have no Hiquphon project in mind -- but a search could give some ideas...)
OTOH, a likely target for mid (I'd suggest a mid-bass unit) could be in the Scan speak range (say a 18w8535-00 or the Kevlar 21W8554 OR the seas/excel W21EX).

An UNUSUAL approach however, would be to try a large diametre wide-range drive unit (e.g. supravox 215gmf or 285gmf -- there are many others). Putting a lot of work (& fun!) into the design, you could approximate a very wide range speaker of exceptional musicality.
On the down side, many wide-range drivers have very high sensitivity (+6db over the Hiquphon) that will have to be matched to the tweets. You will also be able to play with a higher x/over frequency if you wish, and make the hiquphons' life easier.
Good luck!