Depends.I concede I don't know squat about plated tank needs so please correct me if I'm wrong, but aren't under gravel systems also dirt cheap, effective and good for planted aquariums? I didn't mean to insinuate that AC and other hand filters are a bad cheap choice as I use them as well as nitrate filters and they can be had for near nothing used. Just don't want to see you go cheap on a canister filter which deals with water pressure and possible flooding if you go cheap. For the price of two Rapids you could buy a Hot Mag or Mag 350 on eBay and almost forget about your filtering issues and concentrate on your plants. I think those Rapids will keep you busy in fixes, don't skimp on canisters, better to buy used quality then new junk.
I've used UGF/RUGF filtration with plants and had no problems as long as I didn't try to move certain plants. My cryptocorynes, for example, were so tangled up in the plates that it was impossible to move them without harming the existing root system. Didn't end happy for the plant.
One thing to consider is that an UGF will be powered by a powerhead, an airstone, or something of the sort, which will most likely cause some surface agitation. You could try to mod it with the AC HOB driving the system but I'm not sure if it would be worth the effort.
A RUGF would work much better, as it takes water in and pushes it through the substrate. No surface agitation.
But I agree that generally with filtration, what you buy is what you get.