question for marantz AVR setup

[reyz]

pardon if the question is a bit of a noob one but..

i have an issue with the crossover settings for the sr-5003!

the thing is.. when i go into the receiver menu, the only adjustment i can find for the crossover frequency is only one LPF/HPF frequency figure to adjust.. yes, it says 'LPF/HPF' but not seperate individual adjustments for 'LPF' and 'HPF'.

however, after some thorough reading of the manual, i deduced that it must most probably be the HPF (this is because the manual notes in this section that "If using small front speakers, set a slightly higher frequency. If using large front speakers, set a slightly lower frequency")

so, assuming that the LPF might be on my subwoofer instead, i went to adjust my subwoofer's crossover frequency knob to "roughly 120Hz" for a decent crossover slope. then i read my subwoofer's (a boston cs sub10) manual and found out that the crossover value is only activated if plugged in to the line level inputs (L-R) on the sub, not when plugged in to the LFE input.

so im slightly confused... now say if i choose to plug in to the LFE input only, then where on earth would my LPF be??? if i assume that the receiver's settings mean that both LPF and HPF are simultaneously set at 80Hz, then wouldn't the crossover on the sub be meaningless (as only freq below 80Hz would reach the sub anyway), assuming if it even worked in the first place?

and btw, how can the only crossover option on the receiver be to set both LPF and HPF simultaneously at the same value... wouldnt that virtually eliminate any crossover slope if your speakers were set to Large?!

if thats not the case... then where is the LPF for my sub?

hope anyone informed can help me figure this one out! im looking at setting my fronts to Large (which i already have) and having a HPF for them at 80Hz and for my subwoofer to handle all LFE and freq below 120 Hz as well.

my speakers freq response (+/- 3dB) is below:

flstanding fronts: 46-25kHz
centre: 80Hz-25kHz
rears: 120Hz-20kHz

[edit]
and to add.. my manual describes the SPEAKER SIZE settings as these:

LARGE:
The complete frequency range for the channel you are setting will be output from the speaker.

SMALL:
Frequencies of the channel you are setting that are lower than approx. 80Hz will be output from the subwoofer.
If the SUBW is set to "NO" and the front speakers are set to "LARGE" then the sound will be output from both the L and R speakers.

in the preference setup it also indicates under "Audio" setting whether to set to Main, Sub or Main+Sub. According to the manual, "in the audio mode, dolby digital and dts output is set to either "Main" or "Sub". "