Welcome to the forum, Eric. The first thought that came to mind in answering your question is the same as Bob's: using the DS864. I know; it's a bit of a hassle mapping 20-30 samples across in the sample editor, and it sure would be simpler to just drag 'n' drop them. But the advantages are that you're not limited to one-minute .wav files, and that you can do some extreme processing 'in-house' while routing the results to eight different outputs. You can then set up eight FX chains for each output to augment the 8 processed 'streams', and further sub-mix those in the 4 Aux busses.
But I'll also offer you some alternative approaches. How about using two instances of Cyclone? That'll give you 32 pads to work with, each with (potentially) its own output? With careful mapping, you could trigger both instances from a single MIDI contrller (and MIDI channel), and reserve a different MIDI note# for each sample. In a similar vein, you can use two instances of Velocity, and trigger your samples from the 36 pads available to you; mapping them in the same fashion. Here you'll be limited to routing to 5 outputs (per instance), but that drum synth has a more natural feel to it IMO for sample triggering.
One more way would be to load the samples into 30 tracks of the Groove Player, and use MIDI Remote Control (say, with Note On) to bring the track volumes in & out. But there are many disadvantages to this procedure. First, CPU usage. The MIDI Remote control will also swing your levels from Inf. to +6dB, which will cause distortion without some careful post-mixing. You'll be limited to 1-minute .wavs here, and with 30 GPs, you're just
asking for a corrupt file due to the Groove Player "non-bug".
The truncated files that you've experienced might be from using one-shot [non-Acidized] .wavs which don't neatly conform to the ".wav pattern" container. Have you tried dragging the end of the .wav in the Tracker? As for a third-party solution, the one that comes up most often is
sfz from rgc:audio. You can't get that kind of quality any more inexpensively than with this one [it's free]. HTH