I liked the flexibility of lifegard systems, but I don't think they are too popular. All depends on what you need. I feel most canisters have decent bio, and good mech, where a sump is 99% bio and usually a lil something to clean particulate. If it's just bio you need look into a bio reactor or moving bed filter
try looking on amazon.com for a rainbow lifegaurd fluidized bed filter for the biological side of filtration - very inexpensive for what you get and maybe the rest of the modular system likebrich999 suggested