Welcome to FlyerTalk, Hey Look Pal!

I think Aegean can be good for some people, but probably not you -- you say you don't have time to use lounges and don't fly internationally much, so it's not going to give you the biggest benefits. I'd leave that aside for now.

You should absolutely get the US Airways credit card. Use it once and never again, and it still pays for itself: you get a lot of bonus miles when you sign up, you get 5000 miles off of award redemptions (so a ticket that would cost 25k will only cost you 20k if you are a cardholder), and you get 10k bonus miles every year you hold the card. There is a $89 fee after the first year, but even if you think about it as buying 10k miles for $89 it's not a bad deal.

So what else should you do?

I would think of it this way. You should (a) build up airline miles (b) build up hotel points (c) maybe some misc stuff (cars, whatever).

You have a good start on (a) through your regular flying. Your 150k currently, plus the sign up bonus, will get you to 200k, which can get you round trip to Europe in business class.

For (b), I would suggest either the Chase Sapphire Preferred or the Starwood Preferred Guest card. Virtually everyone you ask will say these are the #1 and #2 best "day to day" cards (which is #1 and which is #2 might vary based on who you ask). The CSP transfers to a number of hotel programs, so you have flexibility on where to stay. The CSP also transfers to United (Star Alliance, like US), Korean (SkyTeam), and British Airways (oneworld), so you have access to all 3 major alliances.

The SPG card limits you to Starwood, but Starpoints transfer to a huge list of airline programs (including US) at 20k:25k -- meaning, if you transfer 20k SPG points, you get 25k US (or AA, or whatever) miles.

The biggest downside to the SPG card is that the sign up bonus is low -- only 25k right now, and very very rarely, 30k. The CSP will give you 40 or 50k. (Note that both cards have a minimum spending requirement to 'unlock' all the miles, and the SPG card has a higher requirement.)

If you apply for one of these two, plus the US Airways card, you will be well on your way to a very nice vacation/honeymoon somewhere, all without going crazy with credit cards, etc.

...

More likely, you will apply for a couple of cards, get hooked, and be applying for 4-6 cards every 91 days and all of your friends will think you are slightly crazy

But that's a discussion for another day.

To recap:

1) Absolutely apply for the US Airways Mastercard
2) Apply for either the CSP or the SPG cards. If ambitious, apply for both.

Unsolicited advice: keep the Amex Plat. There are ways to effectively reduce the rate to $250/yr (using the incidentals credit), and it has some side perks that can be very useful (including US Airways lounge access).

Good luck!