Either of the Port Orleans Resorts will be very close and much more economical than paying cash for an SSR studio. As TDC Nala suggests, you can have your luggage transferred between resorts for free. We have done that a few times when we did split stays. Also, a cab will be under $10 from either POR or POFQ to SSR, we have done that a few times and its easy and cheap and much quicker than doing the bus or boat route back and forth to get between the two.
If you are staying on points and a
DVC member, I belive you get 25% off rack rates if you need to add a cash night to a DVC reservation. If you are renting points from a member who does nto have enough points for all your nights, you might try to find another member to rent you enough points for that one extra night. SSR is one of the easiest resorts to get into on points so as long as someone is okay with a low point reservation (and many are since they have just a few leftover points they'd like to rent) you could do that.
You definitely have some options of staying in the area cheaper or staying at SSR for lower than rack rate.
Good luck with making it all work for you!