little advice needed befor buying D.piano

[pikachu]

hi:)

well...i need portable digital piano for learning and maybe teaching in the future so it is important that the key's will feel like piano more or less (what they call scaled hammer action i think) and also i would like to have abilities to preform live.

my budget is not high and i was thinking about privia px-350,but i went today to a local music instruments store and i had the chance to try privia px-135 and also yamaha p-105 and the px-135 sounds like a toy near the yamaha p-105,the yamaha sounds much better but for it's price it gives a little if you compair it to the privia px-350 and according to that i have few questions:

1.since i cant hear the px-350 live (the local shop don't have it),do you know if the privia px-350,sounds better than the privia px-135? or it is the same sample for all the privia lines?

2.is there a kind of usb sound storage that i can connect to the privia px-350 to add better piano sounds? (i am not talking about midi vst, i mean some kind of audio portable sound bank box)

3.do the key's sensitivity working while playing midi vst instruments too? (i mean in general when it comes to digital pianos)