I went the DIY route and am glad I did, not only is it a lot cheaper it will also be cheaper in the long run. Reason for that is I put it all together myself so if anything goes wrong I should be able to fix it, another thing is when it comes time to upgrade I will be able to do that.
Now steppers V servos, I am not able to answer as I just have experience with steppers. I dont really know enough about it to argue for one or the other but I will say that I use steppers on my Bridgeport Series 1 CNC and have never had a problem. I use 916oz/in and a 2.5:1 reduction and there is more than enough power and I have never even been close to stalling them.
What you will need for a CNC control is a drive for each motor and a power supply to power them. It is also best to have an optically isolated breakout board to connect to the parallel port with.
You can get drives for servos and steppers from www.geckodrive.com and www.rutex.com does them for servos.
Breakout boards can be had from www.pmdx.com , www.campbelldesigns.com , www.cnc4pc.com etc
For the control software there are quite a few, I use Mach3 and I think its the best but thats just my opinion.