BTA would be my first choice for the true perc, but only in a 29 gallon tank, no smaller, but thats my opinion. I don't think any anemone should be in nano tanks.
Neither of you have a tank large enough for a carpet anemone.
Sebae's are very difficult anemones so I would not go that route either unless you have metal halide lighting.
Haitians are a possiblility but I firmly believe you would have better sucess with Bubble Tip Anemones.
Tank should be up and running for a minimum of 6 months, one year would be better.
BTA's can host a veriety of clownfish, including Percs and False Percs.
Thomas