So, since quite some time ago i lost a damn good auction on B52 im still in need of an amp.

Reading quite a lot of various info(trustworthiness of it is different matter) and getting a lot of different opinions on same things(it sill do that great/ its really bad for this and that and so on) i decided to get a modeler that should serve me at least until i get to know some of the amps better myself.

Now i've been reading a lot of positive things about pod hd series and im 80% set on getting HD300/400, just a couple of questions to ask the owners:

Can you play through it without amp?
Im thinking:

Guitar --->POD--->Headphones

Does it have some sort of dedicated power amp (i think ENGL E 530 has one built in although its just a preamp)?
Will following chain work?

Guitar --->POD ---> Cab

or this is necessary?

Guitar --->POD --->power amp/ head/combo ---> Cab(exclude cab if combo)

How does the built in pitch shifter work? Never used any pitch shifter so im total noob in this category. Can you get a bank (or few) of pitch shifted tones for,say, lower tunings (B, Drop A, whole octave lower etc...)?
Does it have any effect on tone?much, at all?

Worth getting 400 over 300?

Sorry for wall of text and meh engrish

Thanks to anyone who will take their time to answer