??? How Much Would You Spend ???

Tough to find a consensus because we have different budgets and spending priorities - those with larger budgets would usually spend more than those on a more restricted budgets. Rough guess those on a tight budget 3-7k for electronics (pre+amp) and those with loose wallets 10-15k+. Above this amount speaker upgrade becomes an attractive budget alternative.

Amplifier is the most important component after the speakers. At least 50% of the cost of the speakers should be invested in an amplifier and you have to not only look at cost - matching amp to speakers is critical. Rarely any other component will make as much difference as a carefully matched high quality amp.

Systems are called systems for a reason so they should be built holistically - a chain is only as good as it’s weakest link etc.

Or you could go for a pair of Dutch & Dutch 8c and call it done.

@freediver "smallish room" (whatever the hell that means), "no eye towards any future upgrade", etc., my recommendation would be to start with matching the power source and speakers.  You'll have to juggle the ratio on that one.  However, that being said, I'm fairly certain you'll end up spending more on speakers, any way you cut this cookie!  Speakers, after all, are the business end of any sound system.  As to how much to spend, and what the ratio will be between power source and speakers?  Well, that is a decision only you can make.  What to buy?  Again, only our ears can tell you that.  Let your own two ears and your wallet guide you.