Speaking of the TX20, there are regs and octopus on eBay at the moment if you do a search for "Apeks". I think it's LeisurePro selling them (they sell on eBay), and I haven't seen anyone bid on their previous TX20 auctions, so you might be able to grab a first and second stage with octopus in the two auctions for about $230 shipped. Then you can add the console of your choice, or just an SPG, and a seperate wrist mounted computer or bottom timer with whatever your remaining budget allows. If you're only doing recreational diving, it's not a bad idea to just use an SPG and bottom timer/depth gauge, and use the PADI RDP or whichever tables you were taught during open water. Cheap and educational.
Apeks regs are great pieces of gear - if you're looking at buying entry level gear, pay an extra $50-$80 and go with the Apeks - the TX20 is the same design as their higher end cold water regs minus "bells and whistles" such as user adjustable second stage, and environmental sealing on first stage. They will last you a very long time.
yknot raised a good point about other gear - regs, BC and exposure suit are definitely high on the list of priorities when it comes to owning your own gear, but talk to a dive shop and see if they can put a package together for you if you need the other items. Shops can often offer finance as well if you have the means to service the debt.