423 IS the right area code for knoxville...
FYI: 9040 Executive Park Drive is a virtual office like Regus (Limbaugh advertiser). From http://www.freemanwebbcommercial.com/freemanwebbcommercial/Page.asp?id=8:
The 9040 Executive Suites ( Knoxville, TN )
"The 9040 Executive Suites provides the complete office without the cost of staffing and office equipment. We understand your business will vary in nature, so we tailor our services to meet your business needs."
Back to Mr. Irion. Here is the up to date contact info: Law Office of Van R Irion, PLLC
9040 Executive Park Dr, Ste 223
Knoxville, TN 37923
Phone/Fax: (865) 622-9674
Email: van@irionlaw.com
BTW, it's not uncommon for attys to live in Chattanooga or Nashville or Memphis, but rent an office in Knoxville. If he's still using a 423 area code on that website, I have to assume he actually lives in upper or lower (but not central) East Tennessee. Possibly the 423 fax number is for his home.