There you go - just buy Mo's spare car - job done!
But FWIW - my thoughts anyway:
Being a Mercedes mechanically, as a general rule, higher mileage Crossfires are a pretty safe bet, as long as they've been serviced properly - so you can get a bargain sports car that will give you little trouble - but if you do have problems, this forum is the perfect place for help!
Mileage also has a bearing on whether you want it for weekend fun or daily use - and how long you intend keeping it.
Of the two you've mentioned, I would look first at the one on Autotrader - it's lower mileage (still a good thing if you can get it, despite what I said above!), with FSH and looks very tidy - but, these days, the camera can lie - nothing like seeing it 'in the metal' - it's got a few little extras like chrome grille & side strakes and c/f-effect centre console kit - quite smart - but just check out that poor wing/bumper joint on the O/S/F - also the higher-placed CROSSFIRE lettering on the boot is not typical of a 2003 car (usally it's along the lower edge - and only higher up like this from early 2004) - so possible signs of repair - not necessarily a bad thing but check them anyway.
Not saying there's anything wrong with the Birmingham one but for only a little more money, you might do better.
You haven't expressed a preference for auto or manual - unusually, the auto is a little more economical.
With your budget obviously you're looking at earlier cars so, while the Crossfire does not have a reputation for rust, there are just a couple of areas to watch: on rear wheel arches - even careful owners don't always keep them cleaned out underneath - and most have a little rust round the boot latch - not a problem and easily sorted.
Some owners have reported signs of rust under the doors behind the weather seal - just pull it out and have a look - not usually bad but should be caught early to avoid trouble late on.
Also watch for water under the boot floor - easy fix, just pull one of the rubber plugs underneath (two each side, the centre ones are at the lowest point) and it will just run out - quite important as there are a lot of electrics under the boot floor.
Even my 2006 SRT6 (29k miles at the time) had several litres in there - I was amazed to see it run out onto the drive! - luckily before any damage was done.
None of these things need be a problem as long as you're aware.
And just exercise the usual caution you would for any used car - good luck and keep us posted!