Yeah..keep your good bike like it is. Precisely because fixies are so simple and primitive, you can generally get away with using old cheap stuff to make a conversion and it will work just fine. So you are better off buying an old beater that you can convert....it'll cost you about the same as converting you geared bike...then you'll have both. To save money do a google search for rotafix...many people here will tell you that you will die with a rotafixed hub, but its not true. I;ve been riding one successfully for nealry 2000 miles. If you find you like fixed, then splurge for the track hub.
I love ridig fixed, but I would never want to commit 100% to riding fixed...gears are great too and its nice to have two or more bikes so you have some day-to-day options.