I know exactly where you are coming from... I live in a apartment too so I have to be careful with what I buy.... floor-standing speakers are a no-no for me so I'm limited to standmounts, the initial problems I had was to stop the bass traveling through the floor-boards... I was advised to fill my speaker-stands with an appropriate filler, which I did but although I did this tweak I still had a lot of bass traveling through the floor... I was going to rip the floor up and put a load of cork under the boards but I saw some granite-bases for sale on ebay for £150 and then read what this guy was saying about it improving bass travel in the floor... I wasn't stupid enough to pay £150 for what is essentially two concrete slabs so I went to a local kitchen supplier who supplied granite work-tops and got him to make me a pair for £35 (exactly the same as the £150 ones), I also bought some spike shoes... the end result was pretty amazing in truth, I had killed 90% of the bass traveling through the floor but there was an added bonus, the bass was more defined and actually came out of the speaker if that makes sense, resulting in a far superior sound altogether.
With my old Arcam-Alpha-10 system with Monitor Audio GS10 (difficult speakers to match) I swear you could actually feel the bass hitting you in the face (air pressure?), obviously I have happy neighbours now and it also means I can have my music a tad louder when they are at home without offending them... having a pretty good relationship with my neighbours (this wasn't always the case) they now inform me when they're out for a few hours or more, this is where I'm in my element music wise as I can have 'live' albums at a reasonably high level where the detail and power comes to the forefront & you just sit there with a massive smile on your face enjoying your music.
with regard to computer speakers... have you ever thought of going with 'near field monitors' instead?... there would be a big increase in music/sound quality.