Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
A few thoughts for you:
On a 20 gal tank, you really don't need a more expensive canister filter - an Aquaclear 50 HOB, or even a AC 70, will be ample to do the job, for quite a bit less $.
As Dog said, the lighting you mentioned is way too much light, even for a 20 tall. His suggestion of 28 watts would be ok, although you could do with somewhat higher intensity lighting - up to 40 watts NO, or less with HO.
No need for a CO 2 system for a 20 gal tank. You can still get excellent results with a more low-tech set-up. Seachem Excel & good ferts, either dry or liquid, can do a good job for you.
Save yourself some $, so you can complete all your equipment needs within your budget, e.g. test kit, some hardscape, plants, substrate, vac, bucket, fishnet, thermometer, livestock, etc., etc.