Merlin's Mk.Ia with model modification is a great choice. Aeroplane Heaven's Mk.Ia is also another good choice.
If your looking for a Mk.II, get Merlin's
Merlin66 has done the most complete set of Spitfire Mk.Vs for CFS2, including a rare Mk.Vb trop with the Abunkir filter. Bruno's Mk.Vc quad cannon, and Vb are visual masterpieces.
As far as a Mk.VII, get Paul Rebuffat's, and when it comes to Mk.VIIIs can't go wrong with either Merlin66's or Paul Rebuffat's. I have both. Paul R did a Mk.VIII with the option to have the engine with 25lb boost, or a basta configuration.
When it comes to the Fw-190 lashed up killer, or the Mk.IX again get both Merlin66's and Paul R's. Then you will have a great collection of both MK.IXc and Mk.IXe aircraft along with high fighter and low fighter sub-types.
Paul Rebuffat has done the only Mk.XII for any simulator I know of, and when it comes to the Mk.XIV, I go for Paul R's.
There are two Mk.XVIe examples I'd recomend, both Merlin66's and Paul R's. Paul's is a razor back example, while Merlins is the bubble top example.
As far as the Messer's
Emil types (E-3,E-4, and E-7), I recomend Aeroplane Heaven's along with Maruo's. (He did an awesome Hurricane collection too!)
For the Fritz, Paul R's are my choice for both the F2, and F-4 along with Jabo sub-types.
Gustavs Paul R's agian for the G-2, G-4, G-6, G-14AS, and G-10AS. (He also did a G-10 with the DB605D engine, but I don't know where to get them)
Konrads, Paul R did the best K-4 that is currently out to the community.