1) i have an xda 2 mini and it has a wired stereo headset that came with unit and it's a 2.5 mm jack compatible with the old xda 2's headset... so you can use it as an mp3 player... it doesn't have a 3.5 mm jack which is the standard for mp3 players... it uses the standard jack for phones (2.5 mm)... but the headset quality is great and if you want to use a high 3.5 mm headphones, you can just use 2.5 to 3.5 mm adapter... and there's a male jack too, so you can connect this to the home stereo system
2) the speed... it actually has a faster processor than the xda 2... which had an inte xscalel 400 mghz, the mini has an intel buleverde with 433 mghz speed... the amount of ram makes a difference when your installing large programs... but you can use an SD card for that... it also becomes apparent when you're multitasking... so close other large memory resident programs before you use another one. and it has 64 mb ROM just like the xda2 but it has 64 mb RAM unlike the xda2's 128 mb... but you can upgrade the RAM if you really want to...
3) wifi isn't built in but you can you can use SDIO wifi card and if you need memory... you can use the Sandisk 256 mb + wifi card which is compatible with this device! (the only pda phone that's compatible with it.)
..... please make sure about your sources before you make an assertion about a device... thanks
and yes all o2 asia products are unlock regarding networks and it has built in program for configuring it with either globe or smart or even sun cellular... (i'm using the unit supplied by smart with my globe sim card)