Bicycle Mechanics - Rear wheel or new bike for trainer? Please help.

I have a Cannondale CAAD6 and sometimes am limited to riding on my Cyclops trainer due to our weather or watching the kids. The rear tire is getting chewed. Thinking of either a rear wheel to swap out, or maybe a cheapo form BikesUSA or Bikesdirect for about $350 that I could pop on and leave there. Having some challenges with the rear wheel. Do I order a rim and just cassette? And if so what size to fit my Tiagra 9 speed rear cassette? The LBS gave me a price of about $250 for rear wheel/cassette/tire all assembled but I just need something to grind on. No luck on Craigs list. Any thoughts? I figured if a rear wheel/tire/tube/cassette would be $200 I might just buy a cheapo bike and leave it on there and replace the rubber as needed.

Any 700c rim laced to a 8/9/10-speed Shimano cassette compatible hub with 130mm spacing. In other words: a standard rear road wheel. Should be able to find a wheel on CL for pretty cheap.

Don't worry too much about quality. Your weight will be supported by the rear axle, not the rim. Even if you can't get it as true as you'd like it, just open the brake up while on the trainer.

If I were you, I'd get the same range cassette as the one you use on the road.

There is no need to drop $350 on a new bike to be dedicated to a trainer. Watch Craigs List or visit thrift shops for any bike in about your size and dedicate it to the trainer. You should get away for $50 or even less.

Weight, brake and shift quality and frame material are non issues since you won't be riding it on the road. Fit a saddle that you like and adjust the position to match your road bike. If you need to change the stem, bars, etc., buy the cheapest heaviest you can find.

My first trainer bike was an old department store quality Schwinn I got used for $35 and put about $25 more into customizing it to fit.