the a2's are highly dependent on positioning to sound good, otherwise sound a bit lackluster compared to their high price, and if you pair them with too large of a sub they might get overpowered given their fairly modest output.
want bass? i would go with some decent sized bookshelves and decent subwoofer. my suggestion would be some unpowered bookshelves paired with either an amp or budget receiver and paired up with a decent subwoofer. decent power output bookshelves will deliver some decent mid bass on their own with the subwoofer filling in the lows.
pioneer bs22's aren't bad for a low budget
klipsch kb-15 icons arent bad as well if you like brighter more energetic treble.
pioneer, sony, onkyo all make decent low end receivers. i would suggest a 5.1 model since it has a subwoofer connection right on it for ease of connections though you could always go with a 2.0 stereo receiver (they are cheaper) although you will need to watch out for low wattage output and you will need to splice in the subwoofer connection on the input signal so connectivity isnt quite as nice.
as for subwoofers, polk makes a few nice ones although i would have a look at dayton as well. their subwoofers are fairly cheap yet for the price are not half bad at all.
if you can find decent output powered speakers (i'm thinking at least 75w) you could pair them up with a 150-200w subwoofer fine. if you get 85w speakers or so you may be able to pair them up with a 300-400w subwoofer without them being overpowered. also, bigger bookshelves would be a better choice paired with larger subwoofers than would small satelite sized speakers.
as far as what i'm using.. i have klipsch satelites (quintet iv) which are rated for 100-120w output paired up with a 450w klipsch sub. balance between the two is fine although i'm lacking just a bit of mid bass by going with satelites instead of bookshelves which the subwoofer isnt fully able to fill in. i did not have the budget for larger speakers at the time though.