For '01, and I'm pretty sure other years, the ashtray light is NOT always hot. It's switched just like the standard power outlets, although it is on a different circuit.
The least expensive modification would involve simply running an always hot lead to the center outlet (properly fused, of course). However, this has the disadvantage of eliminating the controlled outlet. This is sometimes nice for particular uses, e.g., my GPS unit will automatically shutdown when connected to external power and the power goes off.
A simpler modification, and not very expensive, involves installing additional outlets under the driver's seat and tapping the power from the power seat circuit(s). See my write-up in DIY Modifications.