Best way to have heat 'down low' is to not let it leak out 'up high', but I'm sure you know that.

1. What kind of insulation is in the walls above ground? For an alarming number of homes from that era in the Midwest, that answer is 'zero'.
2. What is the condition of the windows?
3. Can you feel a difference between floor level and ceiling level in your basement?
4. What is the ceiling height in the basement?
5. Are the basement vents you mentioned at floor level or up high? Heat supplied up high will stay up high.

"Best" way to have good heat in a basement would be to rip up the floor and put hot water in the new slab, but that's not a practical solution, I'm sure, though you would probably notice some benefit upstairs as well. 

If #3 is a yes, and #4 is enough, a ceiling fan could help circulate the warm air better. If a typical low ceiling, a floor fan tipped straight up could help determine if you have a supply problem or a circulation problem.

If #3 is a no, then electric baseboards are maybe your only option.

I'd be nervous about a gas fireplace in a basement. Beginning of too many sad stories.