Subwoofer volume too low with SBLive!

I have a SBLive! (not 5.1) with Mecer Speakers (Model: SP-128) and a Mecer Subwoofer (Model: SW-128). Previously I had a SB Vibra 128 and had no problems with sound output.[OS=Win98, VIA Motherboard, Celeron 400MHz CPU, 128Mb RAM]

Now, I’m happy with my speaker output volume, but the subwoofer volume is way too low.
I’m sure that the subwoofer is working fine, ’cause I’ve tested it with other sound cards and systems.

Could my SBLive! be faulty?

To sum this up: The only problem is my subwoofer has low output volume.

Have anyone experienced this before?
(I don’t want to solve this problem by bying Cambridge Speakers – or should I?)

Please help.