How to audition used speakers???

A second system, in a dorm?

You will have to save up to get good floorstanders. Even the low end is higher than that. Once youve at least doubled and more likely tripled your capitol. The only way to "audition" anything is to listen to them. That is by definition what you must do. If you want a bewildering array of current production speakers go to an audio show. You will hear a bunch but but that will eat into your money. I would go the garage sale route if I were you. It's hopless witth just a couple of hundred. A decent pair of input tubes cost that much.

Your best bet is to use your ears...locate a pair of the speakers and listen to them...better yet, listen to them with the amplifier that you are buying. Klipsch may not be the best bet with Onkyo...the Japanese electronics have a bit of high frequency bias and the Klipsch speakers, being very sensitive, might emphasize the bias. The Spicas are definitely darker, and while they may work a little better with the receiver, you may be disappointed down the road and the resale value might not be as great as you might wish...if you desire to trade up. You might consider a pair of B&W 302s for a dorm room...these were $299 brand new (Stereophile budget component of the year in 2000), image well, and can be had at a fair price. Yes, you trade off some bass response, but your receiver will drive the 302s without breaking a sweat. When you can upgrade from the receiver, then make your investment in speakers. There is a good resale market for the 302s...you can nearly sell them for what you paid for them...providing you take care of them.

I am a big Spica fan, but I would be hesitant to put them in a dorm system, unless you are sure you can keep someone from cranking them to 11. They are very different than floor stnading Klipsch speakers. They will sound much more natural, but not nearly as powerful, no matter how much amplifier you give them. One of their shortcomings was what the designer, John Bau, called dynamic compression, by which he meant that as you turned the volume up past a certain point, they didn't really get louder, but compressed the sound more. TC50s were the first speakers I bought, and at the time, they sounded so far superior to anything else I heard, there was no contest. Even by today's standards, they sound great. I do remember turning up Talking Heads and Yello fairly loudly with no damage, and liking the sound, it is a very clean, non-fatiguing, controlled sound, but not nightclub / bar room sound. Replacement drivers are no longer available, so if some knuckleheaded friend of a roomate does something stupid, yuou're out of luck, unless you buy another pair for parts.
It's interesting that Dphd mentioned the KEF 104.2s. If you can find and afford a pair, this might be a better choice. I remember hearing them in a store at the time and thinking they sounded kinda like my Spicas, but with better bass, and presumably more ruggedness.

My humble advise is to never buy speakers without hearing them driven by the power amps one intends to drive them with ultimately (period). And in the same room you plan to put them in, if possible.

Yes, I know this is more difficult and sucks but, not as difficult and sucks less than repeatedly being disappointed and continually flipping gear that doesn't have synergy yet, everyone agrees is (individually) a very cool piece of gear.

This is experience speaking and you probably will not know the difference unless you try working out your system in this way. LOL

Happy Listening!