I went through the same decision earlier. Basically, I was looking at three options for a den/nearfield setup:
1. Swans M200s
2. Bookshelf speakers (Von Schweikert VR 1 or Totem Model 1 Signatures were my main targets) and sub (probably an Onix Rocket UFW-10). I'd also need a decent amp and maybe DAC. For the amp, I was looking at the Rotel RA-02 or Arcam A65 integrated amp. A Jolida JD1501RC hybrid integrated would be nice as well.
3. M-Audio BX8 130 watt bi-amped studio monitors
I went with option three because I'm not ready to sink the dough (even w/used stuff) I would need into option 2 above at this time. If you want to spend the money though, I would go with a monitor setup similar to option two (there are plenty of good speaker/amp choices out there). The Swans can be found for around $185 and will probably need a sub to go with them to match the bass of the other options. They were very tempting but I went with the BX8's on closeout (last year's model) from Musiciansfriend.com for under $300 shipped. They have 8" drivers in them so hopefully I won't need a sub. I'm also messing around and getting back into playing the guitar again (via GarageBand3) so maybe the BX8s will work well for my needs. I haven't had a chance to hook them up yet but am going to try to in the next few weeks. I bought some 28" Sanus stands for the BX8s as well but may just put the monitors on my desk/table w/some Vibrapod cones underneath them. Once I get everything hooked up, I'll report on the sound. Basically, is this the best sound I can get for under $500 or do I need to go all out with bookshelf monitors and an amp for den/nearfield listening?