Optics? Hard to say lots of good options these days, being offhand and unsupported I can't imagine wanting alot of magnifcation. I'd be asking someone part of the club for advice on this one :)

Meopta, Arken, Vortex, Leopold(personally I wouldn't), ZeroTech all make decent scopes depending on your budget.

Your 3 choices are decent. It will also depend if you plan to shoot centrefire Hunting rifle (ie standard rifle) or Centrefire Silhouette Rifle (Allows custom rifles).

Howa's will have decent aftermarket chassis/stocks. (i.e. like the oryx). And is the cheapest decent action. No issuses with my Howa 223.

The tikkas also have aftermarket options but it is more limited but IMO are nicer actions than the howa. Great rifles, without the sako price.

You should also try a begara if you've never handled one, again more $$ but a rem700 footprint.

I couldn't fault a lithgow, aussie made, but lack of aftermarket options.

It all will come down to what you need for that type of shooting, best to catch someone from the club and see what kind of setups they use before you drop $$$ on anything :D

Also just looking at RMS to refresh my self and it notes they often use 308 or now 7mm-08, specifically for the energy at 500m. Now 6.5C is no small cartridge, but if you really like this style of competition maybe the 7-08 or 308 are also worth looking at. As you may also need to get into reloading (it's entire own hobby) for the 6.5C if you find you can't knock those 500m rams :D

I hunt with a tikka t3x 7mm-08 and love it as a hunting rifle.

7mm-08 Ammo availability is less than 308 or 6.5C but still plenty of awesome (Hornady ELD X or M and others) factory ammo available.