Pulaski

Agreed on AMEX, agreed on xe.com, not agreed on CU's - they may be cheap and cheerful but no substitute for a proper bank. I agree with the recommendation for Wells Fargo - notwithstanding some BE members' negative experiences, WF has scored consistently well in the national customer satisfaction surveys for several years, often ranking No1. Also it's branch network is as wide spread as any bank's, from California and Washington to Florida and Connecticut (though missing Boston and the rest of New England), and covering more than 30 states, including a large presence it Texas.
HSBC is unlikely to be much help as it's branches are almost entirely confined to New York

On taxes, you can probably save some if you can wangle a move in late April or early May, because you'll get the full 2013-14 allowances, but only have a few weeks pay to set against them, so you should be able to get all or most of your PAYE tax refunded.

MsElui

when we came over we were desparate to buy but couldnt find what we liked and ended up renting. It REALLY worked out for the best though as it allowed us to get used to the specific area and fine tune it better to suit us - as well as understand the differences in our life better so we could get a house style that would suit OUR new style better (by that i mean - it IS different to the UK and initially you try and replicate exactly what you had before. if you spend a few months settling in and working out what changes you will end up making - youll find houses better suited to the new stuff.

newadventure

RE: Bank account
We were in same position. Not moving over permanently, so we have kept the First Direct account, but used it to open an HSBC account in UK and USA before we came over. It was useful to have the account up and running before we hit the tarmac, as it were. Also able to get a proper credit card with a reasonable limit, albeit not the (frightening) limits we were able to get in the UK.
We got the Premier service, so ATM withdrawal charges get refunded also the Global View which allows you to see UK bank account alongside US bank account. Very easy to transfer money between the 2, but expensive. Use an FX broker (we use Halo) instead

SSN - don't apply as soon as poss. I did this and then had to wait 7 weeks to get my SSN. As they mention on the forum, wait 10 days before applying.

Don't know what age your kids are, but there are lots of resources available to help choose schools, and then you will need to decide whether to keep them in their 'UK year' or with similar ages

Good luck and have fun