I may shortly be upgrading my Q6600/Ati 5850/4Gb RAM system to one with a bit more grunt, which I hope will last me 5 or 6 years. Unfortunately, finances mean the odd compromise, possibly even the entire build itself 
I would like to base it on this bundle from OCUK
Intel i5 4670 at 4.2Ghz
16Gb RAM (I'm looking to the future with this)
Asus Z87-K Intel Z87 (Socket 1150) DDR3 ATX Motherboard
Paired with a Radeon 290 such as the Sapphire TRI-X, a cheap as possible 24" monitor that is still ok, a cheap as possible SSD of 200GB+ capacity.
I'm content with the CPU+GPU+RAM, but the costs of the other items are pushing what I'd like to spend. So, a little few questions I'd value some input on:
1. I have a decent, new 2Tb HDD already. Will I totally ruin my PC experience by not having an SSD to save money?
2. What's the best 24" monitor in the sub-£150 bracket? Presumably they are all 1900x1200
3. Is there a cheaper mobo than the one in the bundle above that will allow an easy overclock on the CPU? I'm not really a power user of motherboards, but would like decent onboard sound if possible.
4. Is there any decent compact case that this would all squeeze into? I realise the graphics card is pretty hefty.
Cheers for thoughts on any or all of these questions.

I would like to base it on this bundle from OCUK
Intel i5 4670 at 4.2Ghz
16Gb RAM (I'm looking to the future with this)
Asus Z87-K Intel Z87 (Socket 1150) DDR3 ATX Motherboard
Paired with a Radeon 290 such as the Sapphire TRI-X, a cheap as possible 24" monitor that is still ok, a cheap as possible SSD of 200GB+ capacity.
I'm content with the CPU+GPU+RAM, but the costs of the other items are pushing what I'd like to spend. So, a little few questions I'd value some input on:
1. I have a decent, new 2Tb HDD already. Will I totally ruin my PC experience by not having an SSD to save money?
2. What's the best 24" monitor in the sub-£150 bracket? Presumably they are all 1900x1200
3. Is there a cheaper mobo than the one in the bundle above that will allow an easy overclock on the CPU? I'm not really a power user of motherboards, but would like decent onboard sound if possible.
4. Is there any decent compact case that this would all squeeze into? I realise the graphics card is pretty hefty.
Cheers for thoughts on any or all of these questions.