Good to hear you got a result there, SRP's pretty sh!t hot...
Keep in mind though that SRP has a lot of fillers in it ( forgot to say that before

) meaning some of the swirl marks you had will still be there and when the polish starts to deteriorate ( which all polishes/waxes do ) you'll see them again..
To prolong the affect of your polishing, I'd put a couple of coats of sealant and or wax over the top.. ( sealant for a silver car had been recommended to me time and time again )
Regarding other polishes - other than machine polishing, I've heard Megs SwirlX is supposed to be pretty good...
Here's some pics of my Silver 1.8T ( crap quality though - mobile phone pics ) and more info re waxes etc..
http://www.detailingworld.co.uk/forum/showthread.php?t=123241Don't know much else I'm afraid...