What do you mean your dealer can't give you a demo unit?? I hope you're not thinking about cashing out money for a small car without having a chance to try the product out and making sure you're making the right choice. That would be unprofessional. The dealer may need some kind of reassurance that damage won't be done to the unit, or if it happens that he can charge you for it, but otherwise it's in his best interest to give you a demo. If he still doesn't want to, talk directly to the manufacturer.
As for putting the unit on the air, you don't necessarily have to do that. If you have an unused transmitter or exciter you can feed it into a dummy load and so transmit a very low power FM signal to listen in-house on receiver(s). You can even compare that with your on-air signal, though in comparison keep in mind that transmitting chains are not exactly the same. The dealer may arrange that for you. Put it all in the flight case. That's what I did for some customers.
I would advise against making any purchasing decision based on subjective and individual opinions on forums. Those can be very misleading. Not to mention how the input you get will greatly vary on who is present on the forum, what their preferences are, what their experience is with different products or in the field in general, what brand they might be cheerleading for and just plain statistics and probability. Lets hypothesize there are 90% of people buying product A and 10% buying product B. You go on the forum and let's assume it just so happens that there are only people who like product B there. You get rave reviews for product B, you think those 6, 8 or 10 people can't be all wrong, you feel confident that the product B is the right one. But is it? Did you get an objective picture of the whole market? You didn't. The number of opinions (which are, again, subjective) you may get is way too low for any relevance, not to mention certainty. That's why when you do polls, you have to do it on statically relevant sample, otherwise it's false. This is a bad poll...
Regards,
Goran Tomas