I would start looking for a used FEC100 - those can be had for under $3K usually. Outside of that, A wholehog is great. I have used one in competitons for several years now. I cook in mine no less than 100 times per side per year. And it has held up great over the years.
An insulated cooker of any type however will really help you with fuel consumption and time/temp mgmt. Spicewine has a model that will fit in that range I believe as well.
Good luck on your search!!! I'm happy to answer any questions about my pits.
Andy /Smoke on Wheels Competition BBQ - www.smokeonwheels.com