I have a PS3 and PS+ [...] memory card wont be a problem as i will get a bundle AND my brothers 4g memory card, as well as a 16g card within a month or so.
What the hell are you waiting for ? Get a Vita and a *32 gb* memory card. Forget about the 4 gb memory card, you can keep them to try Japanese demos if you so wish but that's it. I wouldn't bother with 16 gb cards either, they're overpriced and it sucks but 32 gb is small enough as it is. Just my $.02
Thing is, none of the next-gen phones are going to be anywhere near as affordable as the Nexus 4, they're all going to be in the $600 range, with the possible exception of the next Nexus phone that comes out (they've been doing 1 every year). Even that isn't a guarantee, since the previous ones weren't as cheap as the Nexus 4 when they launched, IIRC.
If you have $300 dollars to spend, get a Gameboy Advance and a few games, and go to the "phone store" of your choice and find a phone that is a few years old, and on sale for $19.99. Less than 50 bucks should be out of pocket.
If in six months you find you are actively searching for more GBA games, and your phone has used less than 100 minutes, get a Vita. If the GBA is buried in your sock drawer, and you are getting out of memory messages on your phone because you have downloaded everything in the store, get a Nexus.