So...I haven't heard the Merlins myself, but based on what you're after—love midrange and soundstage, want more dynamics, need acoustic suspension for close-to-wall placement—Fritz's speakers might be the ticket. I have the Carbon 7 SE Mk IIs and I think they'd be worth considering.
They're at the same pricepoint, hand built in the US. I find the midrange to be honest—instruments sound like what they are, not what the speaker wants them to be. Soundstage has real depth and width and the dynamics track everything from quiet to loud without strain.
For your setup: their benign impedance curve means your Anthem will have an easy time of it. They work well in nearfield and should integrate well with your REL subs if you want.
Fritz is very approachable and works with people. Call or email him. He's direct about what the speakers do, offers return options, and doesn't use a hard sell. Given that you're restricted to online purchasing, that matters.
That's it. I have found that in comparison with every bookshelf I've heard, the Carbons are excellent speakers. Worth the conversation.