Thanks those RSL are exactly the type of thing im looking for in ceiling speakers and are in my price range. That Mk5 sub is hefty for me in price but ill check out the other sub. I may start with one sub and upgrade down the road. Should I stick with the same sub model/brand for front and back? I assume better to have one higher quality sub than two cheaper ones?
Don't think of the subs so much as one "expensive" vs. "two cheaper" - think of them in terms of performance. One well-placed "big" sub might be all you need! The advantage of of two subs is the smoothing of the bass response across a wider area of listening positions. Problem can and often is proper placement of sub(s)! The biggest you can go for your wallet and the space (there are of course practical limits, and you do not need a MASSIVE sub for a small space, of course!) is what I recommend.
But yes - generally speaking, it's a good idea if you are doing multiple subs, to make them the same ones. Starting with one is perfectly fine, especially from a budget stand point. And if you like, it you like it!

If it is primarily you doing the listening, placement is easier - put it where it sounds best to you in your spot. But if you move around a lot, or have lots of seats in the room, you'll notice the bass changing as you move around from place to place. And if that is an issue, then go dual and it will help you out. Lower frequencies are a big part of the HT experience, and you will not regret investing in them.