I don't know of any hosting svcs that are using pHp 5 or MySQL 5 yet. They're just too new and not entirely trusted yet. On the website I administer for my job, I tried pHp 5 but went back to 4.4.4 because of some issues. MySQL 5 has some gotcha's in it also but it is working well now (make sure you take strict mode out of the ini if you use auto incrementing keys!).
As for IX Web Hosting, it looks good so far but I haven't committed yet. Am waiting for verification of what I need in writing right now.
They have 3 plans:
$3.95 - 2 Domains, 100G Web Space, 1,000G Data Transfer, 100 Sub Domains
$6.45 - 8 Domains, 300G Web Space, 1,500G Data Transfer, 300 Sub Domains
$12.95 - 16 Domains, Unlimited Space, 2,000G Data Transfer, Unlimited Sub Domains