Whether it's a good SPL depends a lot on what frequency you're measuring. 102 dB @ 20 hz would be pretty good. The same figure at 60 hz, well, probably enough but not a really impressive figure. Bear in mind that if you stand in 5 different spots around the room you'll get a range of numbers that might be 15-20 dB different. You typically get some room gain at the very low end, and room modes will create peaks and nulls thru out the room.
In my med-to-largish room I can get about 120 dB @ 20 hz, measured in the spot where I do all my listening. I use 2 pretty large subs with a pretty good sized outboard amp to get that, but it's some serious grunt. If you can hit 102 thru most of the range from 20-80 hz, that should suffice for most stuff.