maybe Dan or Rusty can give you better info. But, if it was me, Id just get the Sony with housing. in fact, if you love your tv, which I bet you do, Id probably buy at least 2 more bulbs. Maybe even 3. I know that's a lot of money, but you would be set for the duration of the tv's lifetime.
FWIW< someone who knows a lot more than me about AV recommends buying 5-6. I know, nuts.
We've got a 2yr old Sony KDS50A2000 that has a warning finally showing up that lamp (XL-5200) is nearing end of life. Lasted longer than we expected since our TV is on 8+ hours per day. Our quandry is whether to buy replacement w/housing at Sony for $250 or risk our cash elsewhere for a lamp only (no housing) for maybe $150. Any experience or suggestions out there?