Centrum Dumaguete. Reasonably priced and they use a good installation company. They've just done another 2HP one for me.
Abenson in Dumaguete sells several brands of aircons. Their prices are reasonable and include installation. I live in Dauin so there was a 2ooo pesos delivery charge and an additional 2000 pesos to remove my existing unit. If the installer needs to install wiring to feed the unit there is an additional charge for that.
Good experiences with DuEkSam here. Arguably even more important than the install is the long term experience, which boils down to choosing a reliable brand and having the unit cleaned by professional and reliable people. Your mileage may vary but we had not so good experiences with Samsung units; they were cheapish but didn't last. We're now (the last 3 or 4 years or so) running three Panasonic units, not cheap but so far no issues at all.
We're all Panasonics too. The oldest is around 8 years and never had an issue (also bought from Centrum DGT, and same installer as last one)
Don't forget to factor in the Energy-Star efficiency rating numbers. Many years of use out of a unit is great but more so when it has a lower KWH consumption. Maybe my math is off but this is an example of how I looked at it the last time we bought one. I'll use the 2.5hp needed and the three Panasonic models I found on the Abenson website. The most expensive was 72kphp with a ES rating of 6.81, 209.25kwh per month based on 9 hours daily usage. I can't find my last bill but think it was about 12php per KWH. So 209.25 x 12 = 2511php per month. Let's say you leave it on 24 hours a day like I do. 24hrs divided by 9hrs=2.66 times longer. 2511 x 2.66=6679 php per month. The other two 2.5HP Panasonic models both have a 6.11 ES rating, the least expensive being 62kphp. With the ES rating 6.11 is 243kwh per month based on 9 hours daily. 243x12 = 2916php per month. For 24 hour use 2.66x2916=7756php per month. At 9 hours per day the monthly difference would be 405php per month. The recoup of the 10hphp will take 24.7 months. The eight year difference will be 38,880php A 24 hour a day user is looking at a 1077php monthly difference. They should recoup that 10kphp price difference in ten months. The eight rear difference will be 103,392php. How well the house is insulated, 9 hours, 24hours, price per KHW are all variables of course.