Steel studs for basement, size?

umm i have not seen a metal stud that has not been galvinized or some other rust preventer on them in years. no need to use treated plate just nail the track to the floor or if really concerned about it lay sill seal down first then track. i prefer 20 gauge over 25 a lot stiffer and a lot less deflection since drywall will be hung on only one side.also may want to add stud stiffeners or spazzer bars since board is on one side only. lay out is 16 on center since common metal studs are only 1 1/4 thick not like standard 2 x wood material at 1 1/2. width i would use at least 2 1/2 but prefer 3 5/8 so at door ways you can frame opening 3 inches wider and 1 1/2 taller and wrap with wood to hang door and trim if using standard wood door frame and wood trim. add wood blocking (or something called danback) at bottom of studs if using wood base trim so it can be nailed on tight. and add blocking to other studs as needed to hang cabinets and other items. insulation at box store will not work since it is made to fit between wood studs and metal studs are hollow so insulation is made wider to fit in hollow of stud and stay in without falling out.
to find products (studs,screws,insulation, and drywall) in your area just google drywall suppliers in chicago or metal stud supplier in chicago and find one near you
here is a manufactures web site
http://www.clarkdietrich.com/products/drywall-framing/prostud-drywall-framing-system

As your concrete walls are "wavy", use two layers of 1"XPS rather than one layer. Use a square pattern glue bead to lessen the possibility of basement air to the concrete; http://joneakes.com/jons-fixit-database/743

You will get moisture traveling through the cavity as the foamboard is a vapor retarder, not barrier. Wood framing can act as a hygric buffer absorbing water lessening moisture shock, staying wet and warm until dry (unlike steel- rusts even when warm, if wet). The fastener attachment/hole of stud/track looses the galvanic coating at application, and will rust there. You might try spraying each with a rust preventive or similar. The f.g. insulation batts leave full length chases (inherent to design) for air movement and possibly convective loops around the insulation (depending on temperature differences), be sure to close-off all gaps- no matter how small;pp.4, Fig. 4, convection- pp.5; https://docs.google.com/viewer?a=v&...fBrOrJ&sig=AHIEtbSk4qNS_4vQRnyKBiEiG1lHFDd9yA

Be sure the stud wall is not touching the foamboard for conduction and R-value loss or moisture present there; http://www2.dupont.com/Tyvek_Weatherization/en_US/assets/downloads/Master%20Architect%20Binder/Technical%20Bulletins%20and%20Case%20Studies/Commercial%20Technical%20Bulletins/Tyvek%20with%20Exterior%20Insulation%20Building%20Science%20Bulletin.pdf

The 2" XPS will have a temperature of 40*F (cavity side) for a dew point of 32% RH at 70*F room temp. This using your J, F, and Dec. low temps average; http://www.weather.com/weather/wxclimatology/monthly/graph/USIL0550
Below grade to the "frost line" and above grade.

Use a sill sealer under the plate- wood, metal or composite (60% wood fiber/dough that will mold). It stops air, thermal and acts as a capillary break; http://www.greenbuildingadvisor.com...ressure-treated-sill-plates-and-building-code The steel transmit your room heat very well to the colder foamboard and earth under the concrete slab (55*F) much better than wood (even at R-1.25 per inch) ever could. Thermal bridging, pp. 7, insulation charts- pp. 9, 10; http://www.buildingscience.com/docu...cs-high-performance-walls-limitations-r-value The thinner galvanized coated studs could react with the newer pressure treated wood of today, research that.

Gary