I should cross-post this to the "Do you AAA?" Thread. Penske has a deal with AAA. (At least, with AAA Michigan, they did) I had a move last year from MI to TX that was in your ballpark, list price. The AAA "show your card and save" cut it by 45%. There was a discussion thread about this sometime last summer; some claimed that they could haggle individual store managers to this level, but the AAA pricing allowed me to get what they fought for, without any hassle. And, moving would be the time I would be most likely to save hassle.
I would also point out that a larger van will not be proportionately more expensive to rent. You might find a larger size is less popular, and might be cheaper for you. This is common for rental places, as it saves them from paying to reposition equipment. But if you go up in size, watch the gas usage. And when timing your travel, understand that the trucks will likely have speed limiters on them.
U-Box is fine, works like PODS. But if you have help for a period of time, be sure to watch just how long they will take to get your load across the country. It's cheaper because they are sharing a ride, so it will take quite a bit longer than driving yourself--particularly if the load has to cross through Chicago.