Certainly, do put that extra fridge to good use and by all means store some of your collection in it! Extra refrigeration is a boon to just about any winemaker, wine collector, or home brewer — just ask how hard-core brewers love their “lagering fridges.” I would see if you could adjust your temperature to a steady 52 ºF (11 ºC). This can be done with external thermostats available at most homebrew shops. Even putting the fridge on its lowest setting would be way too cold for properly aging red wines, or even storing white wines. Keeping wines in too-cold an environment can cause an untoward potassium bitartrate crystal precipitation and some suggest it can even ruin the wine in the long run. Keeping wines chilled just before serving is fine, of course, just don’t store wines at these temperatures for too long. With regards to humidity — a fridge isn’t the most arid of conditions, but if you’re worried, pick up a hygrometer (humidity meter) and try to keep your refrigerator as humid as your other wine-storage cabinet. Metering systems and humidification tools can be purchased from the same companies that sell wine-storage units (like the one you’ve grown out of).
For more of the Wine Wizard’s wisdom, pick up the latest issue of WineMaker magazine available now at better home winemaking supply shops and newsstand locations.