I use an Eheim 2075 with my 20gal, although it might seem a bit over the top if you are aiming for a good planted tank you`ll be needing about 10x the turnover e.g. 200gal/hr. Mine does roughly 317gal/hr but don`t forget that manufacturers specs are over the top and never the true value as you have to take gravity, kit and filter media into consideration so my 1250ltr/hr rated filter is actually more like 800ltr/hr when it comes out of the filter.
I love my Eheims, silent, powerfull, flexible and most of all they have never leaked on me. I had a Fluval 405 once, it leaked, i bought an Eheim 2224 and never looked back. Since then i grabbed an Eheim 2078, 2075 and a 2028, all have been running with zero issues. Maintenance wise they are easy as the pre-filter is on the top so you just need to remove one basket and voila all done with no mess etc.
Hope that helps.