A rookie with 10K, seeking advise

Your Wharfdale Linton's are a very nice speaker in their price range so the question I would be asking is does your amp allow your speakers to fill your room with the volume and quality of sound that you enjoy?

The Strata is not a bad integrated and it appears to have sufficient power but if it is not properly driving the Linton's you could also have a problem going to a larger floor standing speaker.

The Ortofon Black is a very nice cartridge for you turntable also.

You’ve been given a number of good suggestions and a number of different directions so you most likely have a lot of thinking and research ahead before you make a decision. When you do narrow down some of the components you are interested in and are looking to the second hand market take a look at tmraudio.com. You will pay somewhat more than buying from an individual but they offer a two week trial period and if you are not satisfied you can return and pay only the round trip freight. 

Upgrade only one item at a time or you won't know the actual impact of the individual items. Speakers generally have the biggest impact and are the easiest to hear a change in the sound quality and should be upgraded first. There are a ton of great speakers out there to choose from between $5 and $10K. 

After that and only after that should you consider upgrading your integrated amp if so desired. Allow the speakers to break in per the required time and then see how your current amp and speakers actually perform together as a system.

Your PS Audio Strata Integrated is a very decent amp at that price level and the rule of thump is you have to spend 2x the list price amount to get a noticeable difference but different amps could also have different sound characteristics so that would also come into play in spite of price.