This is my my opinion anyway, it reaaly is down to personal preferance.
My advice is to go somewhere to actually sit in the chair.
Staples do offer a decent range, although not the cheapest.
I have had at least 10 diffrent chairs over the years, although i dont work in IT (I do spend alot of my Free time in front of the PC).
I have the bottom 2 of my Vertibrea fused together , due to an old motorbike Injury some years ago.
I have suffered from Pressure on the Spinal nerve from a disk injury, although not for some years now.
Part of my problem with my Back injuries is iritated by sitting for long periods of inactivity.
This is eased by choosing the correct chair with a good posture and lumbar suport.
I also have to choose my Cars Carefully, for the same reasons,lol.
Unless you dont sweat at all i would stay away from all Leather chairs.
Leather faced ones (at least the thin budget priced ones) are just cheap rubbish that wears quickly, cracks and splits.
If you really love leather, then buy a Proper but expensive real leather one, not faced!
Leather in General is cold when you first sit on it, although it quickly ajusts to you body temp.
In summer if you sit on it in shorts etc then you will stick to it and wil give you sores if spending long periods in it.
Suede is a good alternative.
The cheaper chairs have badly made gas rams that dont last.
The main point of weakness is the join between the plate where the chair seat blots onto and the Ball joint that goes onto the top of the Gas Ram Mechanism.
This will wear even quicker if you choose a Tilt chair (which i always have!).
It depends upon your body weight and how often you tilt back and swivel.
Im 6ft 2" and weigh about 16 stone.
Im Sitting writing this in a Fabric and Suede Execuctive chair which is 5 years old and has been the most comfortable PC chair i have ever owned!
The mix of Fabric and sude gives your body the correct temp, its never cold, wears better than cheap leather.
Mine was bought from Office World, Now bought out by Staples I beleive.
Viking Direct offer good prices, but its the ame with any online retailer (You cant sit in it before you buy!).
Dont touch anything that PC world sell, all crap and some not so cheap crap!
You could try Argos or Homebase (both part of the same retail giant), but again dont go for the cheap ones.
At least with Argos you can take it back within 30 days if you really find it not comfortable.
You could try
Cheap Laptop, Hard Drives, LCD Monitors, TVs, Televisions, Netbooks and more at Ebuyer.com , as i buy most of my PC stuff from there.
But read the reveiws carefully as to what people find to be a good chair.
I think this applies to Most online retailers, if you can find one that has good reveiws and plenty of happy customers.
I think its the age old moto "You get What you Pay For !"
On a Sperate note for those who suffer back and Neck pain, You should position your monitor With the center of the screen at Eye level.
Most decent quality monitors are height ajustable to acheive the above.
Use a Foot rest which tilts ( i use a Kensinton one) .
Find a PC desk that allows your wrists to sit with your arms level with your keyboard & mouse.
Buy a decent Quality keyboard with Rests that allow your keyboard to be tilted upwards at the back.
I custom built my own PC desk, which is made to suit my height and posture perfectly to reduce RSI, Neck strain and Back problems.