There are a few companies which sell nice units on ebay, like
this one
$150 US for a 5 stage and it includes some installation supplies, a faucet and even some extra filters. Plus it ships from Ontario so shipping will be reasonable and no worries about duty and brokerage fees.
The first three stages are not all carbon, only one, the other two are sediment. Living in Calgary you don't need the 6th stage (DI). You should be able to get 0 TDS without it. It may depend on where about in the city you live but I setup a unit there and the TDS going in was at 54ppm and a normal five stage brought it down to zero and kept it there for over a year with regular use.