Hi Brian and welcome to AH. You certainly have nice L/R/C speakers.
As for Sub: From what I gathered it's 10" driver with 150wr rms amp and in 17liters sealed box
I'd consider that only good fit for small rooms (below 1500 cuft)
Your LCRs drop like a rock to 4ohm impedance and stays there very often:
http://www.stereophile.com/content/martinlogan-montage-loudspeaker-measurements
You should limit yourself to receivers officially rated for 4 ohm speakers or better yet - get AVR with 7.1 pre-outs and use 3 channel amp to power your LCR, while using AVR's amps to power rest of surround speakers
New or Like New Denon/Marantz purchased from authorized resellers have 3 year warranty which may give a bit of piece of mind.
I recommend going with denon 3xxx series or a bit higher
https://usa.denon.com/us/product/hometheater/receivers/avrx3300w
No need to go crazy and get top/near top model - it won't help you much.
Speakers and Sub (yes - mostly likely you'd have to use old sub in the bedroom/office or sell it) I suggest to postpone until you know exactly what is the space you're working with, not trying to retrofit.
But in general subs from HSU, PSA, Rythmic, SVS are better value and performance than B&M brand like REL.
They are trying to bring new budget models to compete with ID brands like I mentioned above and while prices are somewhat compelling the raw performance is not match yet