You are talking $1200 refurbished 3700 ? the next 4K 3LCD option is 5040UB (refurbished, 1080x2 eshifter) for $2500, or DLP eshifters are around $2250 for BNIB as well, so is that a 2x the price worthy upgrade given you are will mostly viewing 1080p content ? IMO no, that $1k savings should be able to get you a BNIB 4K unit a year or two down the road and a quality 1080p unit will be more than enough for now.
With that said, I would recommend considering an extra $300 and getting the 5030 currently on sale @ $1500 instead, at 10x the CR it will make a difference especially in a dedicated HT room (it's also equipped with bigger lens shit so will make placement less of a challenge).
Good luck,