i would suggest either a T5NO (normal output) or a T5HO (high output) if you want your plants to be happiest. 8 to 10 hours a day of light will be plenty with these bulb types.
your lighting is most likely T8 lighting, and if you want to upgrade to T5 you'll need to buy a new light fixture. T5 bulbs will not fit in a T8 fixture. for upgrading lighting cheaply, go buy another T8 fixture and put it just in front or just behind your current one. this will double your wattage if the new light is the same as the old. remember to change your bulbs every 6 months with T8 lighting, to keep it optimal for the plants, and ensure your K rating on the bulbs is around 6500 K (this number is optimal, but you can swing some in either direction of 6500).
the 55 gallon planted i just had regular T8 bulbs on, and the only time my plants really did well was when i had no lids on that tank for a time (but got too paranoid that fish were going to jump out). with the glass lids, plants did ok, but nothing spectacular.
the 20 long has a coralife fixture with a dual compact flourescent bulb in it. i'm actually running a 50/50 saltwater light with an actinic bulb as half the dual bulb in there (these are not cheap bulbs to buy! lol. i got the fixture and bulb for free a while back). plants do ok, but nothing in there is fast growing (most of the plants are java fern and anubias). i dose ferts on a 'when i remember' basis, so the nutrients are not consistent either. i'm more of a 'sit and enjoy my tank' than 'constantly work on it' type person.
the 2.5 gallon just had a 13 watt spiral cfl bulb (like the kind you put in a table lamp). the plants in there went nuts! that photo is from not long after a major trim job. i'll try to find the one where it looks like an underwater jungle.
i would highly suggest dosing Flourish Comprehensive once or twice a week. when i was a bit more regular on dosing ferts, my plants looked much better.