I will cast a vote for the GWS Slow Stick. It was my second plane after re-kitting a Pico Stick. The SS goes together easily, is durable, and flies well, and with an 8 cell KAN 1050 pack will handle light wind. I still fly mine after building several other planes.
That said, be aware that vitually nothing you got with your Firebirds is transferable to the SS... that I am aware of. So the bottom line cost for the SS kit, radio w/flight pack, ESC, 2 battery packs, and a charger will be $200-$250 for new stuff. But of course, all this gear would be useable with most any plane you would purchase after the SS.
If the cost of the above gear is beyond reach, the Aerobird is a 3 channel plane with proportional throttle. (My understanding is the Firebird was a throttle and rudder aircraft.) Many folks have successfully learned on it for about $160. But, it too has radio gear that is not transferable to most other planes. So, at sometime the cash will need to be spent if you stay in RC planes.
Sierra Gold