Great elements but the mix is a little uneven.
The cello side was pretty empty for the 1st minute or so and the opposite side is full of that lovely acoustic. You might consider throwing an ADT (free VST) on the acoustic to get a faux double track panned to opposite sides to fill out the stereo image then pull the cello in a little closer so that it plays almost beside the vocal.
The bowed bass could use a little more definition up the middle - or perhaps some compression. I haven't been able to find a specific VST or even preset to suit cello so it's a trial and error thing.
If you're using Reaper I'd suggest downloading the THD Fish Fillet VST pack and use Blockfish from it as the vocal compressor. It has a wonderful preset for intimate vocals. A VERY little reverb would also sit the vocals nicely. It would be useful to use the same type of reverb across the project so everything is in the same room. There aren't many ReaVerb presets in Reaper but there're plenty out there.
You might even throw ADT on the acoustic to get a faux double track panned to opposite sides to fill out the stereo image then pull the cello in a little closer so that it plays almost beside the vocal.
It might, also, be useful to cut whatever cello frequencies overlap with the bass so that they don't step on each other when the cello pops up.
Finally, a gentle compressor across the mix - in Reacomp the preset Master Buss Glue one is good.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe