Good day,
What offrovering said, only then for Thule!
I've been using Thule since 1984 without any problems what soever!
Sold it for 20 or so years sold Yakima as well just never was able to get a fit kit for any of my vehicles and the unit cost was substantially more for Yakima (only 310 miles from us, versus Thule coming out of Sweden!)
Allot of people will tell you that Yakima "fits better" than Thule, but that is just not true! Especially with the fact that you have roof bars fitted already.
Between the two systems I would leave it up to personal choice. As far as performance is concerned... I would give both 100 out of 100%.
Like I said, I use Thule, 'cause I have a whole roof load of their equipment (No pun intended

!) I have a nice 11 cubic foot roof box that we use when trekking-That thing has paid for it's self. Lockable, watertight. Luggage baskets, bike carriers, ski racks( which I don't use now that I have a ski/luggage box!), canoe & kayak carriers,etc,etc.
I had most of this stuff before we sold Yakima... Why sell what you already bought just to replace it with a competitors product that does the exact same thing?
I ended up being the Thule expert in our shop.
The choice is yours my friend...
Keep in mind that there are several other rack and box manufactures out there as well...
Cheers
Ry'
ps, try
http://www.rackattack.com/index.asp