I'm trying to improve the air quality in my house. I'm located in the Central valley in California which is in the top 10 areas for bad air quality in the nation. Certain times of the year I sneeze almost non stop from the junk in the air. I'm looking to filter the air better and also introduce some fresh air in the house without having to open windows. I have talked to a few companies but it seems like with the economy most are only a shell of what used to be there and only do basic things now.

I have a 1700 sq ft house.
3.5 ton York Package unit on roof and ductwork in attic. It does a good job heating and cooling.
2 existing 20x25x1 return grills. I'm using MERV 6? air filters.
I use a Honeywell enviracare portable air cleaner in the master bedroom with good results but its noisy.

I have 2 bathrooms and an indoor laundry room. The laundry room has a cat litter box. I was thinking the guest bathroom and the laundry room could be exhausted by a ERV/HRV since the fans are pretty much shot in those room anyway but everything I see seems to be around tying these into a split system and never a package unit.

Any help would be appreciated. I don't know if there is someone in my area that I have overlooked or if I can gain the knowledge to work with the local company I do trust to put something together.