I love the fit and feel of my synthetic stocked Tikka.
That being said, if you'd like the gun even more with the McMillian, then go for it. It would be hard for me to have my baby away for 4 months.
If I had $600 burning a hole in my pocket for upgrades on my Tikka, I'd probably get a higher dollar scope. Mine has a Nikon Monarch 3-9x40, but a nice Leupold Vari III or a Kahles, Zeiss or ?? would make it even nicer.
But heck, if I had $600 I'd buy another gun to add to the collection. :grin:
Good luck in your decision, I gotta feeling you'll be happy with whatever you choose.
Steve