So, I have the Roland A-500 PRO (49 keys) and for the most part I like it.  I recently purchased Ivory II and was thinking I could use another octave set of keys.  Do I get the Roland A-800 PRO (61 keys,) or do you guys recommend something else?

I depends on what you like ;-)
 
If you are totally happy with the A-500 PRO you could simply swap it for the 800 and it would be plug and play - ready to go ...
 
I got the A-800 PRO and although I like it for the straight forward way it integrates with Sonar (transport, faders, ACT, etc) and thus gives you another way to control Sonar from the keyboard, I don't like the light weight plastic feel of keys too much ... therefore I got myself another keyboard with heavier keys that gets closer to a piano feel for about the same amount that the A-800 PRO costs ... so if you want a different feel as an alternative, then go for something else and keep your A-500 as the Sonar controller

Well, what did you get?

amiller
Well, what did you get?

I got an A-PRO 800 plus a smaller older noname MIDI keyboard (with no extra functionality) stacked on top in the control room ...then a Yamaha P-35 B (~400€), which is the above mentioned one with heavier keys (graded hammers) for recording more piano-ish parts in the live room (and also for stage use as it is lightweight and rather cheap compared to other stage piano solutions) ... and a Kawai MP 10 piano for proper piano work and composing (I really love the Kawai but it's expensive and heavy)

What are folks thoughts about this:
http://www.sweetwater.com/store/detail/ImpactLX88
 

I just tried out the Impact LX61 - a different keybed than the LX88, but FWIW, I returned the LX61 to the store - I found it too clicky, and playing it just didn't allow me to control dynamics the way I'm used to.  It felt cheap.  I'm holding out for the new Akai Advanced 61 now.
 
If I had the space for an 88-key, I'd probably try out the LX88 - it seems ideal, for no other reason than it's the only 88-key I've seen that doesn't have piano weighted keys.

To play piano, the best solution is to play on weighted keys. It is somehow possible to play on other, but I suggest to visit some store which has them all. Without "reference requirement" (which exists for weighted actions), everyone produce whatever they want, in terms of feeling and size (length). And they all are different, only you can decide what is the "best compromise".

My 800 Pro works just fine.  Having the extra octave is vey helpful.  However,  you could try a different synth and use it with the 500.

I'm in the process of swapping out my existing midi keyboards.  Sold my A-300 and replaced it with an NI Kontrol S49 (I use Native Instruments).  Also, going to be selling my Axiom Air 61 for the Akai Advance 61 soon.  So, I think both the Akai and NI (if you own Komplete 9 or 10) are good keyboards.  Also, I hear very good things about the Akai MPK249 and the MPK261.  Both integrate well with Sonar.  YMMV

The Novation Impulse 61 might be one to consider.  The keys are semi-weighted and it's a pleasure to play.