Hey man, sorry to hear the SP808 fell through, it's an amazing machine. I use Gigasampler and cooledit to do PC sampling but the 808 gives you the ability to create tracks with a more 'performance' feel.
The 808 also has a new utility available to download that allows you to convert Wavs to Roland format and vise versa so now you can take tons of wav files and dump them to the sampler..or even a whole tune you have been working on. I would strongly reccomend saving.
As regards the 505...I've been doing a lot of homework on all the options and I think I'm going with the 505...in all I can some it up as the mags like to dump on the 505 but users love it. Let me know though if you bought the yamaha and how you found it..credit card hasn't been used yet.
Finally, if you're tight on cash and want the 808 you aren;t missing much by not getting the pro. I initially thought you could SCSI out to a CD Burner but it's only to add another Zip drive and as regards the other I\Os..no big loss. Hope this helps.
G