Oh, I think I'm in heaven... Today I received that replacement Sylvania bulb for the 12" strip light, and the color is just SO "unobtrusive" (the best word I can come up with), yet bright. Granted, the tank has to be re-planted and I only added water back today, but I'm already happy with this light. I tell ya - if you can return the incandescent fixture and pay a little more for the fluorescent light, do it.
Truthfully, it's not that much more for the mini Aqualight, but I think 18W over a 2.5-gallon tank is overkill. I've heard all of the arguments that suggest the smaller the tank, the more WPG's you should have... But there was a time that I could grow almost any plant with the 8W on the 2.5-gallon. I'm also partial to the more even distribution of light with the normal fluorescents. Besides, the 6700K Coralife lamp that I use in my Aqualight on my 10-gallon gives everything this sort of yellowish-greenish tinge that I really dislike. Same with the screw-in PC bulb on my 12" incandescent fixture. Granted, I've only heard really good things about the mini Aqualight, so I probably just don't know what I'm missing out on...
I LOVE those 25W Hagen compact heaters. Actually, I've been running some of my tiny tanks without heaters, but the cold water makes it very uncomfortable to prune and stuff. I really don't like that no matter how small the heater, it's always going to take up valuable space in a nano tank. The other option is to use a reptile tank heater and place it under the tank. I've heard of some people using them, but I'm told that it doesn't have a thermostat.
Good to hear that your new little set-up is giving you enjoyment. Happy planting!