Scarab,
Yes you will need a CF card for flashing with SL5500 - I made the exact same mistake as you with mine - but like yer man says, CF cards are cheap now
As for choice of Rom - I have only tried a few, namely Sharp, OpenZaurus and TheKompany
TheKompany rom is my favourite so far as all my accessories worked straight out of the box with this, including getting my aircable paired with my SonyEriccson z600 phone for GPRS connectivity
HTH,
Dtwilson