Martin Logan CLSIIz - adding more bass?

I have a similar system and room. Your goal should be stereo subwoofers, crossed over electronically at 100 hz or less 18db/oct or more. The larger the driver the better - 12" minimum. Taking incremental steps in that direction (use a single summed woofer at first) will get you there. For example, bryston or db systems xover, adcom 555 amp and HSU 1220 or 1225 woofer will stay within your budget. There are MANY other combinations possible, for example the Vandersteen.

i'd suggest a pair of subs crossed over @ 60-70hz, w/a min of 24db/octave slope. i'd also suggest a pair of vmps larger subs. these are *awfully* hard to find used, but even brand-new, there's nothing that approaches 'em at anywhere near the price, even used. plus, their price includes direct shipping. most dealers will discount these at least 15%. pair these w/a decent x-over from db systems or marchand (or some hi-end used x-over), & a good used solid-state amp, & yule be happy. mebbe it'll be a bit more than $1500, but not by much, and at least yule be happy w/the results. i also buy mostly used, but the vmps were a no-brainer, & i've no desire to change (except to upgrade to their most recent drivers, but it's hard to imagine they could be faster/tighter than what i already have!)

i'd suggest a pair of subs crossed over @ 60-70hz, w/a min of 24db/octave slope. i'd also suggest a pair of vmps larger subs. these are *awfully* hard to find used, but even brand-new, there's nothing that approaches 'em at anywhere near the price, even used. plus, their price includes direct shipping. most dealers will discount these at least 15%. pair these w/a decent x-over from db systems or marchand (or some hi-end used x-over), & a good used solid-state amp, & yule be happy. mebbe it'll be a bit more than $1500, but not by much, and at least yule be happy w/the results. i also buy mostly used, but the vmps were a no-brainer, & i've no desire to change (except to upgrade to their most recent drivers, but it's hard to imagine they could be faster/tighter than what i already have!)

What about the REL Stadium? Most CLS owners I've corresponded with claim this is the sub to have.