As another option, I can highly recommend KT Drum Trigger (free) as a very good audio to midi converter for drum triggering. This (and EKit Trigger, mentioned below) already has the filters, etc. built into the plugin (as well as having visual feedback of the sound that is triggering the midi signals), rather than having to use multiple plugins to do the work of a single plugin (and possibly reductin or eliminating a few latency inducing steps?).
http://www.koen.smartelectronix.com/KTDrumTrigger/
This plugin can work well both for replacing drum hits in audio tracks AND for programming drums.
I've used KT Drum Trigger to trigger drum samples by plugging DIY drum trigger pads straight into sound card inputs, and with a bit of tweaking was able to get some very tight tracking. You can also set up a mic and sing the rhythms or bang them out on a table or other surface with your hands or some drum sticks.
Another free plugin that I've found to work VERY well for this is EKit Trigger. It's no longer being developed/supported by the developer, but it's available in his archive here:
http://www.tinbrooketales.com/archiv...vstplugins.htm
Here's the developer's complete archive (more freeware plugins and drum samples):
http://www.tinbrooketales.com/archive/archive.htm
Developer's main page:
http://hem.bredband.net/tbtaudio/
You can also download EKit Trigger from here:
http://mp3.deepsound.net/plugins_divers.php
With my sound card set to low latency (2-5 ms or so), using EKit Trigger, I could get very playable results playing drum parts in via a simple piezoelectric drum trigger stuck onto a practice pad, with very tight tracking, including being able to play in very usable press rolls.
With these plugins, you can trigger any sampler via midi, so you can use velocity-layered sample instruments, soundfont kits, etc.
There are some other free and inexpensive plugins that have some similar functionality to drumagog. There's actually a nice article on this subject (it's actually about drum replacement in Cubase, which doesn't have very good native facilities for drum replacement) in this month's Sound on Sound.