In before Kevin Kennedy finds this thread and starts pimping the Raynor Ergohuman to push his website up the google search list... again...
Anyway, as far as chairs go in the sub $300 range I'd look at the Global Tye or Global Supra X at Office Depot/Staples/OfficeMax.
Tye:
http://www.officedepot.com/ddSKU.do?level=SK&id=404059
Supra X (they also have it in black) :
http://www.officedepot.com/ddSKU.do?level=SK&id=949058
I only saw one Ikea chair that fit your requirements though I can't comment on it's quality since I've never worked with their product line:
Ikea Klappe:
http://www.ikea.com/us/en/catalog/products/20096539
I'm spoiled rotten and get to sit in a Steelcase Leap chair all day, however it's pretty far out of the price range you stated ($800 MSRP) - though I know a place you can get it for quite a bit less than that...
As for desks, I'd strongly advise you look for something with a laminate top versus the typical "foil" faux wood finishes common on the low end Bush/Sauder and some Ikea brand desks. Melamine foil is thin and, while initially "pretty" will wear through after less than a year of using a mouse on the work surface and is prone to scratch damage and bubbling if you leave a cold beverage on it. If you look at most commercial office desks, they use the more durable laminate finishes and normally have a rubber/vinyl strip around the edge. I'd gone through a few crappy knock together desks before I picked up a commercial grade desk with hutch and haven't looked back. Obviously something in a glass top would avoid this problem though it doesn't fit everyone's decor and you may have to add a mousepad to work with your laser or optical mouse.
This looked like a good option with a laminate top though it's not L shaped:
http://www.officedepot.com/ddS...00&N=2314926&An=browse
For some reason there aren't any non-fugly blocky L-shaped desks at the big-3 office stores.
.. I'll keep poking around. I'm the IT Manager for a $100 million commercial interiors dealer so, while not an expert in the products we sell I've got access to some folks in the know. Generally I suggest you stick to brand names like Global, Hon, Knoll, Humanscale, Herman Miller (though I think the Aeron chair is an overrated, uncomfortable pile) and of course Steelcase - our flagship brand. Give me your high/low budget for the chair and desk and I'll see what some of our sales and design folks suggest.