Better Integrated Amp?

The most important part of an integrated is how the volume control is implemented..  You can have the best electronics, etc.. but many manufacturers then use a cheap $5 pot for a volume control.. 
Be sure to understand what you’re getting in the way of a volume control.. it makes a huge difference..

You really should list your speakers and what type of music you play, but honestly, shopping in the $600 price range doesn’t leave you much room. The Denon integrated has been well reviewed, so maybe that’s your best option. There’s nothing wrong with the less expensive integrateds. I have an Onkyo A-9150 that was about $500 that is very nice and includes a phono stage and a DAC which is not horrible. Buy what you can afford and listen to some music. We all need to start someplace. All this said - sometimes we set a price point in our heads that is just not realistic. If you really don’t have the money that’s one thing, but sometimes we just get an idea of what we think we want to spend and it takes some time to get over the sticker shock of what the stuff we want actually costs. It’s all part of the process.

What is the rest of your system? 

Considerations:
   Budget
   Speaker sensitivity and impedance.
   Room size.
   Loudness levels.
   Use of digital as well as vinyl.

Set up wise the turntable is a pro-ject debut carbon evo but I have not got a speaker yet, I thought i would try and figure out what amp to get before figuring out what speaker to pair it with.
Budget wise I'm in the UK and i can get the Denon for £350 which seemed reasonable for how its reviews look, the Vena is £700 but is more like £450 second hand. So thats a rough idea of my price range wouldnt want to go any higher than that unless I really have to.
This is also my first set up so I can always upgrade parts later down the line.
Music will mostly be Indie/Rock/Metal but a bit of other stuff as well, the room isn't massive so it wont need to be incredibly loud. Say this is my first set up so I'm learning a lot here thanks

At your experience level the Denon would be a good place to start and having a new piece of gear with a warranty would let you focus on other parts of the system. Even the less expensive Denon 600E might be an excellent option since it has built-in Bluetooth that would let you easily sample new music using Spotify or another streaming service and its lower price would leave you more to spend on speakers which, in my opinion, would have more of a positive impact on the quality of reproduction.