I have a Pal v9 PS2 with a 160 gb Samsung HDD installed :D Just bought the network adapter a couple of weeks back from the local gray market over here in Mumbai, India. The damn thing cost me $90 US brand new (network adapter only), but I think it was totally worth it :D Just finished playing GOW2 DVD9 ;) Now trying the Titan Mode :drool: These network adapter thingies are going really extinct or somethin so grab one while you can :)
I think you can use an external USB HDD and use
USBExtreme to boot games off of it, although am not 100% sure about it and I haven't really tried it. But from what I have heard, the games run fine but since the USB is only 1.0 (which is pathetic) the in-game movies will be skippy/choppy and the loading times MIGHT be increased but the game will run :), although am not sure of the compatibility of all the PS2 games coz never tried it myself :)
May be you can google for it. Also, I don't have any idea about booting DVD9 games off of the USB HDD using USB Extreme.