Considering winter wheel and tyre combination for the legacy for several reasons. Firstly, not sure what the low profile tyres will be like in snow, not much good probably, and secondly, would like to preserve the alloys for better weather. I would like to get some cheaper alloys, ebay, and get some winter tyres for the reasons mentioned. What has anybody else got that works well? 

These may fit?

 

I didn't think there were any steels for the legacy except outback. Anyone know if there is? 

legacy and outback are the same platforms but different springs giving more lift on the outback.

After doing some more digging I think your wheel set up is 5x100 with an et of 55 so whilst a quick check on those wheels advertised just to confirm that I would wonder if they would clear your brakes so 15" may not be big enough as you  are driving a spec b which is a bit more potent

these are what I was considering for my Impreza with Michelin cross climate tyres

https://www.ebay.co.uk/itm/Steel-Spare-Wheel-Winter-SUBARU-Impreza-16-inch-16-5-stud-x-100-PCD-ET-55-9565/292063784098?epid=1523601817&hash=item44005baca2:m:mfQ-wwDekWK4nsL216u5Puw:rk:1:pf:0&var=591043118897

 

They look interesting wheels I might contact the seller and see if they fit. 

I was concerned about the wheel/tyres clearing the wheel arch, but you mentioned the brakes as well so that's something else I've got to consider.