I used to think that the DMS3 was too overpriced for it's features, but look at what you get:
DVD Region free - no bootdisc needed!
Mega Memory 16 support without the bootdisc!
Can run apps from Memory card
You can get most of these features in a $30 Action Replay, but with the DMS3, you wouldn't need to waste time with the lengthy boot disc.
If you don't need those features, Apple Pro, Duo or the other chips mentioned will work fine.
The Yellow PS2 auto-boots all. PS2, PS1 stealth and DVD movies.