Checked my PW car rental today, and found that prices have dropped dramatically since my first reservation was made. Thrifty had full size rates in COS for around $18 a day. May want to check your reservations.
Just booked via Hotwire a full size car from Alamo at DEN (Wed to Tues) for a a total of $214.45 (including tax). Not sure it was that great of a deal, but seemed okay to me. (Note: just checked cost if booked directly..$224.00. Hence I saved myself two happy meals.)