Two subs, yes or no?

HMM, mono you say..

Let me throw this at you. I have learned I can use my second set of outputs/rcas from the variable side of the mcd201 direct to a sub. If two subs are run in mono does that mean 1 rca (+), to sub 1, and the other 1 rca (-), to the second sub? Does that equate to a mono hook up?

Or do you suggest sticking to the binding posts of the amp for connection, in mono.....

If the pre-amp has variable line outs, there will be a left and a right. In that case, if you run one direct to each of a pair of subs, they would be a stereo pair. However, the pix of the rear apron of your mcd201 here (http://www.mcintoshlabs.com/images/products/MCD201Back.jpg) shows one set of variable RCA outs and one set of fixed. Without an active x-over of some kind, you would not be able to level match the subs to the mains unless the XLRs were active at the same time and either your sub or your amp accepted XLR inputs. Same answer as far as hook-up, tho. You would connect right output (xlr or rca) to right sub and left to left. Alternatively, you can take the full range signal from your main amp and either route it through a sub(s) (with a high pass filter) to your mains, or parallel the sub(s) with the mains by running speaker cables to the sub(s) and the mains from the taps on the amp. I admit, its confusing. If your main use is HT, and if the output (volume) of the LFE track is sufficent, then I would go with a single, higher quality sub. If your use is mainly music, I would go with 2 subs if your budget can take it. Stereo or mono, depending on the equipment you are using.

Hey thanks, and to clarify, the mcd201 can run balanced to my amp (my preference), and rcas to sub(s) simultaneously...

Music 100%, no HT, budget would allow 2 x Velodyne SPL1000's..

Overwhelming yes! Two subs fill up your space faster, and as bass waves move slower, this will make the bass seem lighter and faster, even if you went with cheaper subs. The trick will be dialing them in so that they mesh well with your mains and then making them work in your room so they aren't just "one note" bass boxes.