We live just south of Nashville and built our pool this past winter. We received one quote from a Nashville based company, Premiere Pools that was reasonable but firmly in the mid $40k range for a gunite, chlorine puck, sand filtered pool. Our desired upgrades would've required putting the project off for another year. My wife's parents live in Brentwood near Ravenwood High and they have a neighbor that had a pool installed by this outfit. The homeowners spoke well of the company but of course they had a Brentwood budget.
Ultimately we went with Hunt Pools out of M'boro. Our 36' vinyl pool came in at mid 30's before we started adding upgrades like extra concrete, deck jets, gas heater, cartridge filter, LED light, etc. His basic package would probably satisfy 90% of people who aren't familiar with some of the upgrade possibilities commonly available in places like Florida & southern California, where every other house seems to have a pool. They were also very good at understanding the asthetic look we were going for and staying consistent with that. It didn't hurt that their upgrades were competitively priced. IMO, he didn't make much at all on most of the upgrades and was content with the profit built into the baseline cost of the pool.
I'm not sure how much success you'll have finding a vinly pool under $30K. My neighbors built their pool in 2006 from the same builder we used and their '06 price was about $33K. They got the builders basic 32' kidney, sand filter, chlorine puck system as they hadn't made the transition to swcg yet. Prices have basically been flat. The other thing to note is that we signed our contract Thanksgiving weekend, i.e. the offseason. I don't know what kind of deal you'll get trying to build a pool when business is at it's peak. You might try doing a TFP search as I've come across at least 2 more people from the Nashville area on TFP. One from Lebanon and another from Smryna or Mt Juliet I believe.
Good luck and let us know who you pick.
I've got a build thread in the Under Construction forum. Search "Nashville Suburbs"