Paradigm Studio 60 vs. PSB stratus silver i

I hate to mix things up...and I am familiar with both of the speakers you mentioned(I auditioned them as well)...but in the most direct terms...these are a lateral move at best in terms of the qualities you suggested...I would contact Roy at Green Mountain(look at manufacturer's list on this site) and discuss the Europas....I purchased these...and they have the most stable, 3-d, out-of-box imaging I have encountered...with a very smooth, extended treble...and sufficient bass...but what you are really gaining is the "liquid midrange" sound hi-end speakers bring...they retail for $900 and I havent heard anything above or below from a monitor...there are also Phasecorrect in design...but Roy will tell you more....also...I have an identical sized...with NAD power and a Sony source...I know what I am talking about! Good luck...other choices...
Vandersteen Model one...Meadowlark Swift...

Which ever spk. you decide to buy will sound a heck of alot different than your PSB 500's! These were a very warm/mellow sounding spk. If your associated equipment is neutral or a little on the lean side, you might be disappointed with the way things will sound at first w/your new spks. (Don't forget the break-in time as mentioned above.) You really need to audition in your room to see which works for you. If you listen to alot of jazz, I personally would look for a spk. w/ a soft dome tweeter. Your NAD should have no problem driving either of these spks.

Your amp is a powerhouse, and smooth to boot. So I don't think that either amount of power or type (sound) of power is an issue with either of these speakers. Pick the one that puts a smile on your face when you listen and forget about audiophile issues: follow your heart, as they used to say in the old days...

Thanks for the suggestions, everyone. Glad to hear the my new amp will be able to provide the required power. I agree that the PSB 500's are mellow. Sometimes too mellow, I think.