Hello I need some outside advice before we Drop 20K on this. basically our old mammoth system is 3.5 ton. its dying. Currently it is cooling "okay" but is not really dehumidifying, its running nearly constantly current loop out = 96 current loop in =84 (st louis area, its hot right now) (IR on the metal parts 6 inches from my pumps) 3 companies, 1st only sells climatemaster. 2 sell water furnace this price are within $1000 to 2000 for the CM 2nd vendor one will not sell me a series 7, even the 3 ton, saying we don't have the loop for even a 3 ton unit. so they want to do 3 ton 5 series 3rd (this vender sell both CM and WF) (this vendor does the well drilling for geo in this area) one is recommending the 7 series 4 ton, this thinking is our loops are 450feet and this makes with the current temps we are seeing the system (system was drilled in 1987 and 125ft per ton was used at that time vise the 150 now) 450/125=3.6 ton the 4 ton unit can handle full load and since it variable will not have to run at the full 4 tons, except on the extreme hot/cold days we can run on this for s year or 2 and if it keeps over running the loop we can dill new loops in a couple years at a cost of about $8K the thought is a 3 unit will be undersized and run in stage 2 for a 5 series or full bore for the 7 and not really be efficient house is 2500 sq feet, slab, single story thoughts ?