"I've read I need a SSD for hold'em manager to run smoothly (and I do have a slight problem with that atm, but would like to keep my database of hands tbh)"
ya, SSD is super important, just in general but especially for database functionality.
"I'm not really clued up enough to decide what ram etc would be needed."
More = beta innit
"Being able to hand a second monitor would be extremely beneficial."
This will depend on both the video cards capability (ie how powerful) and how many outputs it physically has.
The one in the link, has 'a pretty good processor', a good chunk of ram, 120 gb hd is not enough imo (windows will take ~30gb if I remember correctly, cue whacking a database and some applications on it and thinking zomg wheres the capacity gone).
The graphics card itself seems to be pretty entry level, however if you don't play any computer games and just want a grinding portable machine then this should probably be ok, not sure on the resolutions it'll be able to support.
Lots of grinders use mac book pro laptops, and virtualise those sites that still don't have pc compatibility (which is pretty easy). They work well for travelling with and you can just hook up a monitor/docking station to them when you get home and have a pretty competent setup.
Something with similar specs to this would be good for you though slightly more expensive that the one in the OP.
13-inch: 2.4GHz
with Retina display
Specifications
2.4GHz dual-core Intel Core i5
Turbo Boost up to 2.9GHz
8GB 1600MHz memory
256GB PCIe-based flash storage1
Intel Iris Graphics
Built-in battery (9 hours)2
Dispatched:
1-3 business days
Free Delivery
£1,249.00
This seems really good value tbh though i'm confused reading up on the hybrid ssd, if those are any good then it'd make total sense to have those over an ssd, not sure about how dbs run off of them though as I have no experience with them
http://www.novatech.co.uk/laptop/range/novatechnspiren1728.html - £745
(Novatech nSpire N1728 - 17" Intel i7 4702 Mobile Processor - 16GB DDR3 Memory - 1TB Hybrid Drive - DVD Writer - Intel HM87 Chipset)
This is a bit more expensive, but pretty boss, paying enough whereby you get both ssd and a larger hd aswell.
http://www.novatech.co.uk/laptop/range/novatecheliten1549.html - £1140
(Novatech Elite N1549 - 15.6" Intel Core i7 4700 - 16GB DDR3 Memory - 128GB MSATA Drive - 1TB SATA Hard Drive - NVIDIA GTX 770M Graphics).
Hope that helps.