May I suggest a venmar eko 1.5 HRV. It's a compact unit that uses variable speed dc blowers and can be setup for many different homes. Because the blowers are variable speed the system can make up for difincies in your ductwork and makes retrofitting it into old duct system easy. There are 3 settings that can be used to size the hrv for your needs up to a maximium of 153 cfm. Because the blowers react to static pressure in the duct work to make sure they deliver the cfm they are set for you can use a smaller unit and be confident that you are actually getting the air exchange required. here's a link to the info page....
http://www.venmar.ca/AfficherProduit...ngue=en&id=124 . Another plus is it's extremely energy efficient compared to a standard model . I have serviced most major brands of air exchangers and that`s the one I recommend most to my customers for its ease of install, low operating costs, and its ability to accommodate many different homes.