Yes, you can do what you want!
The low pass filter is consisting of the 3K9 resistor and the 1n5 cap, in the showed schematics.
But be aware: should you change the value of the 3K9 resistor, you change the input-z and therefore in conjunction with the t-net the overall gain. The input-z in your schematic is 3K9+18K.
So, I recommend to calculate the gain with the excel sheet, available here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=40664&highlight=
Kind regards
Franz
/Edit: be aware of the high pass filter, consisting of 3u3 coupling cap and 3K9+18K.
/second Edit: Sorry, I wrote about 1st order filters...