So, I've decided (finally) to finish the basement. Its a ground level walk out. It has R19 fiberglass batting for insulation.

Now normally one would get as good of insulation as they possibly can and it wouldnt be a problem if they were building new. But I've already got R19 installed. Its paid for.

I would like to upgrade to the spray in polyurethane foam insulation. I've heard it has a higher R value per inch and is more effective at stopping wind. Additionally, it expands to fill in cracks and crevices, and also strengthens the structural integrity of the house. All in all it sounds like the cats ass of insulation.

Now in my case I have to decide if its worth it. I have 2x4 studs which gives an advertised R rating of 21 for the foam. They claim R7 per inch, so straight math actually puts it closer to R24. It costs $2.20 ft^2 to have installed. In my case it would come to right around $375.17 to do my basement, with me doing labor pulling the old batting (Obviously not a problem).

At the end of the day it comes down to this. Is it worth roughly 400 bucks to go from an R19 to an R21 (possibly R24) and have better overall fill of cracks to cut down on drafts? I honestly dont know the efficienies of various R values. If it was exponentially different between numbers, well no brainer. But as it is an increase of 2-5 R value doesnt really give me an idea of just how much better it is...

Also, another option is to rip 2x4's in half and tack them to the studs. This would make them a 2x6 and with foam goes to an advertised R35 (38 by math). This option really appeals to me. Thats a helluva good R value, plus with all the other added benefits of polyurethane foam. But it would cost a bit more as well.

And last peice of the puzzle....This is only going in my basement. My basement is the only room with R19, all the other are I believe R29 (By code, havent actually checked. Going on faith here). So not only am I gaining a marginal increase in R value but I'm also only doing it to one room (Granted, the least efficient room though). Extending out to 2x6 to go to an R35 would nearly double the current R value, but again....Only in one room....

Sorry for the long post, but I am looking for serious answers and obviously that would require all the numbers and the whole story.

So, in the opinion of the great Arfcom hivemind, what should I do? Just drywall over the shitty R19 batt or spend a bit and go with foam?

With the temps that Kansas gets, get all the insulation you can.

Quoted: With the temps that Kansas gets, get all the insulation you can.

Thats kinda what I was leaning towards.
Ultimately I'd like to essentially redo the whole house with the spray in foam. My dad has it and he absolutely loves it. However this would be a HUGE undertaking, as it literally involves stripping every room, pulling the insulation then having them put in the foam then going back and redrywalling it all.
With the vaulted ceilings, this would be a bitch.

But, with energy costs doing what they are.......

Find al the plumbing and electrical intrusions through the floor and seal them with spray foam. Since you have access to the areas, it shouldn't be too hard.

I think this would be more cost cost-effective in the long run.

EDIT

I'm a dumbass! My basement is only R13.

$400 ? Is there a setup fee or a min. fee?  I doubt that they will come out for one room and only get $400.
That price is surely based on a whole house.
If they will come out for that, then i would say go for it. I wouldn't bother with firring out the walls, making them air tight will do more good than anything.