I have a 304, it works really well, tho after 1 year it seems to have developed an air leak (get air bubbles out of it until I play with the hosing)
It is a good filter and not too bad a price in the US. (68$ from PetSmart, 53$ from BigAls.) Tho petsmart is cheaper up here (stupid pricing, I can get a 404 for 120$ from petsmart, 180$ from BigAls)...
Definately worth it for a planted tank, the RenaXP series also has it's merits, both are a good choice over HOB
for planted tanks (it pays for itself in cheaper media, 1$ for floss and bioballs/biorings are permanent and included)
120 Gal SW, 150lbs Prem. Fiji, 23Gal Sump, 2x250w 15K MH, 4x65w Actinic
3 x Halichoeres Chrysus (1 surfed), 3 x Nemateleotris magnifica, 1 x Centropyge bicolor, 11 x Scarlet Hermits, 6 x Zebra Hermits, 40 x Astrea Snails, 6 x Nassarius Snails, 3 x Cerith Snails