Let's see if I can cover the pros and cons of the driveshaft issue:

One piece driveshaft pros:

*Cheap
*Simplifies getting the proper angles

One piece driveshaft cons:

*Can/will hit the driveshaft tunnel - Requires pinion snubber or some method of limiting suspension movement. And/or... you can pay for a skinny CF driveshaft to help the clearance problem, which deprives you of the advantage of being cheap.
*Limits top speed

Two piece pros:

*No contact with DS tunnel
*No top speed limit
*Volvo design original
*Cheap if you mod the Volvo DS

Two piece cons:

*Can be trickier to get the angles right which is important in alleviating vibration
*Center bearing support reliability suspect in high HP applications

I've got a fabbed (non-Volvo) two piece in my car. It works great and I've got a fair amount of power. I would think for a car that's "not going to be a mega-powerhouse, but a daily driver", that the stock two piece would be a good place to start. Shimming the center bearing to equalize angles isn't hard, and I can send you a copy of the sections of the books I used to set mine up.

If you're interested in confusing yourself, you might find the following thread interesting.

http://forums.turbobricks.com/showthread.phpt=22629&highlight=driveshaft+angles

Peter