Yes, the X50. The X5D was based on older 01w and X-series wave rom, the newer X50 is based on the Triton so it's sounds are much newer; it's pianos and strings sound a lot better based on what I heard during the clinic, and it fits well within your stated budget. I like the fact that its a very portable keyboard, the "end handles" are quite appealing, kulang na lang ng handle at the back.
P. Pitch carries Roland (and Yamaha); if you're interested in the Juno-G. The Juno is also a good sounding keyboard and the Juno-G is more of a workstation than the -D version.
Choose whatever keys according to which sounds best to you as long as it fits your needs and your budget. I believe both will get the job done.