I'm with roadie on this one. If money is really not an issue, then get a CompuTrainer. These are great as they allow to program in any workout you want and then the system makes you stick to it. You also get power readings, and can train to percentages of your pre-determined FTP. soooo, much better than turning that resistance knob on a spin bike and training with only a heart-rate monitor/RPE.

Unfortunately, computrainers might run a bit more than $500, but if you can find a good deal on ebay or craigslist, then this is the way to go.