When I approach any project or purpose that will require significant financial outlay, my method is consistent. This has been the case with cars, computers, home entertainment gear, etc...
First, I find out what the ideal solution is from a performance perspective (completely ignoring cost, aesthetics, or other factors).
Second, if this solution isn't within my current budget, I try to determine how long it might take before the cost of the ideal solution and my budget might cross paths (either through me saving or the price declining). I compare that to the "pain" of living without a solution, or continuing to live with my current solution. If that crossing point is too far in the future, I will start to lower the cost, thereby bringing the time horizon closer until I have found an acceptable compromise.
Third, since I share my residence, car, and most other aspects of my life with another, if the solution is a visible one (i.e. not hidden in a closet, the attic, the trunk, or inside the walls) I will (with the other's input) weigh the aesthetic considerations against the established price/performance determination. Here again, if there is a reasonable compromise to be found, it will determine the outcome. However, in matters of electronics, computers, and audio-visual reproduction (and recently in some remodelling), I am usually deferred to, as long as I have given fair consideration to her opinion. If I feel any performance compromise isn't acceptable, she is generally willing to trust my judgement. (Or maybe she just plays along to humour me!)
Now, putting all that into a simple set of percentages is pretty tough, but assuming the process would be the same for an acoustic remodel as it has been for other situations, I'd approximate
60% - sonic benefit
25% - cost
15% - aesthetics
However, in the case of remodeling, I am fairly certain that there are few performance improvements that can't be made aesthetically pleasing with a little imagination.