Hydrogen is the best software drum machine as far as I know. You may need to look around a bit for the right kind of samples for your sound, but Hydrogen will sync perfectly with Ardour and should easily do everything you need it to.
Or, if you want the very best drum sounds and soundshaping possibilities (but no sequencing capabilieties, you should use Rosegarden for that, or Ardour 3) then Addictive Drums runs absolutely flawlessy with Festige or even dssi-vst on Linux.
I like Linuxsampler, and you can even use Hydrogen (last version) to trigger Linuxsampler via MIDI if you like.
That way you can enjoy the HD-streaming capabilities of Linuxsampler and use giga drum samples like Natural Drum Kit and kits from Analogue Drums; and then record every drum item into Ardour before mixing, just as you would do with a real kit.