I've had a set of 559 Velocity Thracians for about 5 years now, that started out as an upgrade on my old StratusXP, and were then transferred to my Xstream26.  They're still holding up nicely, but I'm thinking strongly about going to 650s on the XS for summer / faster riding.
 
It's probably opening up a can of worms, but what recommendations do the racing/rando/fast recumbent masses have to offer, for a 650c wheelset where the rear loading is probably 180 pounds, but won't break the bank?  I'll probably run Terry Tellus 28mm tires...

I've always been happy with Velocity Rims, the Deep V are especially stout, and pretty Aero to boot.  Also had a set Uriels on the Corsa that I put well over 10,000 miles on.  The hub flange broke and was repaired no questions asked, but I never had any issues with the rims.  For my 20" wheel sets, and my 650B wheelset the Aeroheats have been great, so very happy Velocity Rim / wheelset customer.
 
Take Care,
Nelson.
 
P.S.
 
Joey over at Rockwall Cycling is a great wheelbuilder!

Velocity wheels are often your best bets for strength and value, IMO.  I dunno if they make the A23 wheel in 650c, or what your price range is, but I think it would be ideal.

I'm not saying that these are the wheels to buy but they are the ones I have been running on the Corsa since the beginning of last season.  http://shop.bacchettabikes.com/parts/wheels/alex-320-dx-tri-wheel-set-650c.html
 
I got them for a reasonable price of a CA2 owner.  Surprisingly enough my fat rear end hasn't broken them at all. Haven't had them trued either though Jay did tweak the spoke tension a couple of weeks ago.  I'm surpised with only 20 spokes on the back end.
 
I might be interested in trying to switch wheels out with you for a ride if your 559s will fit in my front fork if you wanted to try them out on a little.  I have been thinking of getting a set of 559s.

After busting two rims in two years, Eric at RBM laced in a velocity fusion with round spokes. When asked about weight limits, he said I should'nt have to worry at 200 I'm at now. So far so good.

My Xstream came with a Uriel on the back and something else on front.(can't remember) I like the wheel although I have no other frame of reference. I bought some terry tellus tires after reading rat rider's review but I'm running conti gp's on it now. I'm thinking about putting a tellus on the Uriel and leaving the  skinny tire on front. Maybe I should mention that in a separate thread. I like the Uriel wheel though and would recommend it.
 
I wanted to add that I had thracians on my SXP and was happy with those wheels too. It's hard to compare thracians on the SXP with 650s on the Xstream because the Xstream is just plain faster.