It doesn't look like Push bothers with bare bones Fox Floats. The lowest level Fox on their website is Fox Float Rs.captain spaulding said:I say choice C. Send it to PUSH and have them rebuild/tune it.
If you get a new rear shock it's not necessarily going to be tuned for your Rush so it might actually feel worse than the stock shock. Of course buying a new frame is an option to, but a bit pricey esp. if you like your Rush and it's not that old.. Sending it to Push is the cheapest and I think the most logical route..
http://www.pushindustries.com/ for more info