By now, most Pro Tools users realise that "native" versions will always be limited. Whether it's I/O or track count, you have to spend a lot more money on an HD system to get what you want. There is no middle ground. It's $3000 or $30,000.
So when I came across this, I was salivating. That's right... read your way through the first few pages.
An M-Audio ProFire Lightbridge with Pro Tools M-Powered 7.3, 7.3.1, 7.3.1cs1 or 7.3.1cs2 will give you 32 channels of simultaneous I/O, not the limited 18 mentioned in the disclaimer on the M-Audio website.
Thanks to ebay and willing sellers, I have Pro Tools M-Powered 7.3.1 and a ProFire Lightbridge. I can confirm that this combination will indeed record on 32 tracks simultaneously. Since I have no A/D converters, I haven't tried this with actual audio signals feeding the thing.