My current setup is using a Windows laptop and desktop running independently (laptop for Serato - desktop for Resolume Ave). Controller-wise I have a Numark Mk2 and an APC40.
Couple of issues with this setup but the main one for me is portability. Taking this big desktop (originally a gaming machine) to gigs along with all my other gear just isn't working. Really liking the idea of being able to take one computer that can cope with running Serato and Resolume.
Price of course is a factor but I'm thinking a 21.5" iMac or a Macbook Pro. Don't know Apple but it's time I did. I will only be buying for this work however, I won't use it for anything else so don't want to spend anymore than I need to. At the same time, if I'm yet buying another computer, I want no regrets. Really want to get right first time.
Be really interested to hear from people that use both Serato+Resolume off one machine.