hey, it might be possible that satanico wants a near silent system. don't know about all phase change setups, but i hear the promethia isn't that silent.
anyway @ satanico
if i were you, toss the BIX, i know it is tempting and in europe it is hard to get anything else. but you can buy a perfekt new heatercore from
http://www.dtekcustoms.com/ or wreck an old car and grab one yourself for some really low €€.
if u want submersible pump, take a look at the new low-cost eheim products. they are being sold in local aquarium stores, they do 1000lph at 20W at 2m head. they are about 5 x smaller than a eheim1250 with allmost same specs (and did i mention they cost about 4 x less than the eheim 1250 too?)