The USB-6009 has a maximum aggregate sample rate of 48 kHz. That means that the sample rate per channel is 48000 divided by the number of channels. If you use all 8 channels, the maximum rate per channel would be 6 kHz. 12 kHz is the maximum you can expect with 4 channels.
I cannot tell from the data you sampled at 5 kHz what the spectrum really looks like. The data looks suspiciously like it is undersampled. Can you change the acquisition VI temporarily to record just one channel at 48 kHz? Then record the raw impact of your hammer and post that file. The filtered signals are irrelevant at that point. Then someone can probably advise you on the sample rate you will need.
Lynn