yeah, unless you're getting some really, really small speakers (and i know you're not), that fixed crossover shouldn't really be a concern. most speakers, bookshelf or tower, unless they're really exotic, strange, or bizarre are going to work fine with it.
capeche? this is discussed, with graphs, in the HT beginner's primer, in the section about crossovers, if i'm not mistaken. if the inflexibility of that arcam's bass management crossover frequency bothers you, then i'd seriously consider something else. i just bought a 3803, myself; $899US...