S320 1999 Bose upgrades

Hey,
I'm new to this forum so Hi to all!
My Merc Bose audio sound system falls short (way short!!) on bass front. Any body else facing the same problem in an S320?

I'm now planning to add two subs (500W each) & an amp without letting go of the stereo. any one know what's the best around (within $1000)?
tx.
Would appreciate brand specs & details for reference.