Almost each vendor out there states "handling any data sets!". The question is just "how"..
Obviously, the ways differ. To make sure it will be really working as expected lets check how it is imported and build a couple of reports. What do the biggest players offer?
I think 20 000 records is heavy enough to check the level of capability to handle such data volumes, so the customer can sleep well and be sure that even though the data volume grows with the speed of an avalanche my app is (and will be) ok with it.
I will focuse a spotlight on: