10" subwoofer around $500, used or new?

I'm looking at a 10" sub for a 20'x11' room (in an apartment, hardwood floors).
Mostly for music (and 5% for movies). 

How much has technology improved?

Should I got for a used $500 sub which were original $1,000+ ? Eg: 
- Rel strata
- Boston PV1000
- Totem Dreamcatcher
- MJ Accoustics 100 Mk II
    ** OR **
Today's subs around $500 new will give a better sound? 
- SVS PB1000 10"
- Martin Logan Dynamo 
- Klipsch R10SW 10" 

Any other suggestions for new, or used sleepers to look out for?

Thanks!