I used a compact on the death ride, with a sram 12-28 cassette on the back. And saw plenty of compact cranks on the DR, many equipped with a similarly large cog in the rear!

This got me to within one gear inch of my granny gear on the triple with my old bike and I needed every gear inch towards the end of my death ride. That said, I lost the gear increments in the rear, as the cassette goes from 25 to 28. So if you like having incrementally close gear options (25, 26, 27, 28 in the rear), I'd say stick with your triple.

Regarding use of Mt bike bogs in the rear- this only works if the bike has shimano components. Campy and sram will not accomodate the larger cogs. It's pretty expensive to convert to a triple and many frames will not permit the conversion. If you want a triple, it's probably a better idea to buy a bike that comes with a triple.
good luck! the felt sounds sweet!