The IDA-8 and P3's pair great together, though both of those two pieces have preformed well with any other gear i own. I've had the IDA-8 hooked up the the C7's, 30.1s and P3 all for extended periods of time and have zero complaints.
As far as any other LS3/5A clones go, I don't really like the Spendor's and while the P3 is in the tradition of the 3/5A its moved well past it in my opinion. Personally i love the speakers for what they are. The other mini-monitors i would look at would be the ProAc Response DB1.