Installing hardwood in basements can cause problems because it is prone to expansion and contraction with moisture levels. You need a very dry subfloor to install the hardwood on. Engineered flooring is a good alternative to hardwood if you want to keep the look. That said, here is how I prep a basement floor.
The critical first step to installing any basement floor is to address any moisture issues before you begin. If you have visible moisture anywhere you will need to take steps to correct this. Drainage is a discussion to itself so I will leave it at that. Even if your floor appears dry I recommend taping a 2x2 sheet of clear plastic to the floor and leaving it for a couple days to see if moisture forms on the underside. Remember, it's cold up North right now so the moisture level could be deceivingly low.
My preferred method of installing a subfloor is to install a layer of 1" extruded polystyrene foam(tongue and groove edge) to cover the entire floor. Fill the spaces where the foam meets the basement wall with Great Stuff(foam insulation in a can). I tape the seams of the XPS foam with tyvek tape to make a tight vapor barrier.
Depending on the amount of headroom you have(this is a code issue so measure before you plan) I will either directly apply the subfloor at this point using tap-con screws or a powder actuated nailer or install framing members which are called sleepers. For hardwood flooring the sleeper method would be preferable. You can use 2x4 or 1x6 pressure treated wood for the sleepers, whichever is more affordable and works with your headroom. You can also rip the 1x6 in half. Install the sleepers at 16" intervals, on center, with either powder actuated concrete nails or tapcon screws. The 3/4 inch tongue and groove plywood should be installed across the sleepers so each 4' seam is on a sleeper. You must use either galvanized or stainless steel screws to attach the plywood because of the pressure treated studs. I also recommend using sub-floor adhesive. Viola! you now have a warm and dry subfloor to attach your hardwood to.
In all cases you need to level the floor with a product called levelastic. Very important step... do not overlook. It is a very free flowing cement product that gets rid of all dips and valley as well as being self leveling. When leveled install a vapor barrier.
Scenario number 1 you create a wooden subfloor to nail into and install any hardwood floor as instructed. The problem is your are going to raise the floor by 4-6 inches and lose some height to the area you are installing.
Scenario number 2 consider a floating floor. There are manufactured hardwood products that glue or click together and do not require nailing. I don't believe I have seen a solid hardwood that you can do this with but I can be wrong. The manufactured floor is a real hardwood on a substrate base.... usually the hardwood is 1/4 inch thick or so. here is some interesting info on floating floors... http://www.hardwoodinstaller.com/hardwoodinstaller/floater.htm
Hope that helps,