IMO...
The v6 can tow a decent amount just fine. I tow a trailer with about 4500 lbs worth of lawn equipment 3 to 4 days a week and have been doing so for the past 3 years.
I think it'd be much cheaper to just upgrade to stainless steel brake lines, buy a trailer with trailer brakes, and/or possibly upgrade the pads on the T4R.
And you can still lift the SR5 with a little less difficulty than the Sport Edition, all for $160. I'd go ahead a lift the rear as well, especially since you'll be towing a travel trailer
Amazon.com: Daystar KT09115BK Comfort Ride 2.5" Strut and Coil Spring Spacer Kit: Automotive