Efe
Suggestion for you here -- Spend a very few $ and get Ed Frias to mod your BIC crossovers. It's a MAJOR upgrade. I just got my pair of DV62CLR-S speakers done and let me be very clear, they're a whole new set of speakers. Best $40 I ever spent on audio. Before, I felt they were an OK set of cheap speakers, nothing like audiophile quality, definitely not good enough to use in my studio or HT. They sounded harsh, messy, undetailed, hard on the ears, generally unpleasant. Now, they're clean, accurate, detailed, and VERY pleasant to listen to even at high volumes. I'm actually in the middle of a mix using them in my studio right now and I'm thrilled with them. They're not as smooth or warm sounding as the B&W DM602 S2s I use in my HT but for the price they're fantastic.
I know you wanted in-walls or in-ceilings, but for the best sound you might consider moving your 62si pair to the back for surrounds and buying another pair of 62CLR-S for mains. I haven't heard the sis but I'm sure with the dual drivers the CLR-S will give you a bigger, fuller soundstage in front.
As for a sub, I haven't heard the Dayton or the Advent, but I can recommend the XSub for a budget sub. I like the one I have. But personally, if you have the patience to wait and save up, I'd wait and get an SVS PB10-ISD. The difference is incredible. Matched with an all-EFE-modded BIC system, you'll have a HT setup that will shock and amaze you and your friends for a price no one will even believe.
Hope this helps.