Two couples are celebrating our 50th birthdays this spring w/a trip to NYC. We'll see a play and do museums, but my husband really wants to hear live progressive-rock or classic rock, preferably in a fairly intimate setting but larger venue ok too. Any suggestions on how to track this down, or clubs to check? THANKS

The Village Voice paper is a good source for all sorts of live music listings. You can search by date, type of performance, neighborhood, venue etc. on the following link.
http://www.villagevoice.com/nycguide/index.php?sid=6

For prog rock, classic rock etc., I like the Bowery Ballroom. A mid-size venue. I've seem some great shows there. But I wouldn't limit myself to just the Bowery Ballroom.

http://www.ohmyrockness.com/Venues.cfm

Check out the web site of Time Out New York when you get closer. They list what's on at all sorts of clubs and small venues.

And don;t forget to check out the Beacon Theater. Not small- but gets some incredible performances - often with unannounced people sitting in.

http://www.boweryballroom.com/

Apropos the Bowery B/rm. We went there a couple of years ago to see joan Baez. We didnt understand the comments about getting here early etc. etc. Till we realized there is no seating. So we hurry up to the balcony so as to see better. There were 4 or 5 chairs up there. A railing to lean on (or sit on the floor behind)and some heating or A/C equipment to sit on. So, be prepared. Joan was great.

See if anyone he likes is playing at BB Kings while you're here. Sometimes they have a Led Zeppeling tribute band. The place is expensive but the sound is great.

also check out JOE'S PUB
great showcases
very intimate setting