SummerAttire.com - if I am not mistaken ''attire'' is the word used in British English primary. If so, you limit your market significantly (especially with .co.uk for the UK's market). On top, selling only summer clothes (if in the UK)? Summer there is like 15 days, 20 if you are lucky. Anyways, not so thrilled about a name.
MagicMailbox.com - could be a name for companies that produce and sell mailboxes for private houses. Specific but has a chance. High to mid $$$, imo.
AlphaHeights.com - mountain climbers niche. Possibly. Same, mid to high $$$.
ManageRevenue.com - accounting/financial advising niche? Could be... Same as above.
ExpressThemes.com - can't really see a value here.