I have gotten a few estimates to replace my entire 16 year old heat pump and air handler. The existing unit is a rheem 2.5 ton 10 seer heat pump. The company that I liked the most out of the 4 that came out to give me an estimate quoted me for a 2.5 ton 14 seer unit and also a 2.5 ton 15 seer unit. The other companies quoted 14 seer 3 ton units but I did mention to them that that's what I was looking in to. The house is close to 1800 sqft 2 story with 10 vents down and 5 vents upstairs. Should I consider another 2.5 ton or go up to a 3 ton? It's important to also point out that I have a very tight space to install the air handler and every one told me only certain units from what ever Brand they use could fit up there. The trane guy said he would make the opening bigger to install a 15 seer trane up there if I wanted that.