If you want to timbre match, that would be tough. IMHO, timbre matching the rears isnt critical. the centre ( if there was one ) would need to be though, but thats why I'm recommending skipping it
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I use a Pair of Floorstanders for fronts , and some small satellites for the centre and rear. While it isn't tibre matched, it sure sounds better than the sattelites alone.
Similarly Superczar here also uses Floorstanders for fronts , a timbre matched front, and an old Hi Fi system for the rears. If you're using the A2's , and if they are kept close together , then you dont need a centre
I'm not sure how the A5's compare with the A2's . if they yield more bass, then yes, they are better for HT duty, but I've heard that they're more of the monitor variety, so no.
But dont the A2's Have enough bass as it is ? Either way, if it doesnt , Use a 5.1 speaker system, and use ffdshow/your soundcard ( if it can) to filter the bass from all the channels and to the sub