You're lucky to have a great amp for the job, just checked out the spec on that amp and the XLRs on the back are power amp pre-outs. Your bacon is saved and knowingly or unknowingly you've bought the perfect amp for the job!
You need to connect XLR to XLR between the receiver and your speakers and you should be set to go...
HOWEVER, a couple of things to note before you do. Firstly, most powered speakers have a volume control AND some form of equalisation on the back somewhere, have a look for this, if that IS the case (which it probably is) then the first thing to do is turn all the equalisation OFF, (you have a perfectly good pre amp that is going to do all this for you, if you equalise it twice, it's gonna sound BAAAAAD)! Secondly, before you switch anything on, turn all the volumes down..... A LOT.... they should pair up quite nicely but in my experience of powered speakers, they very often tend to have a further pre amp in them meaning that if you have the volume turned up on the actual speaker you could potentially end up shoving up to about 10 times line level (pre amplified music) into the installed amplifier - this means it will desperately try to output 10 times the volume level as well - not a very clever idea!
It'll be a case of turn things up gently on your powered speakers until they match the rest of the system sensibly - then turn up the volume on the receiver. This way you're going to get the result you want without finding speaker coils embedded in walls on opposite sides of the room!
It should all work great so long as you're careful - let us know what happens.