By loss of power do you mean slipping? In my experience clutch slipping is your last notification of impending total failure
In the past (with my other cars) i've found GSF to be the best price wise and never had a problem with any aftermarket item from them.
just a little note:I’ve noticed a lot of people swear blind by OEM equipment. My dad drives his A4 hard and changes his front & read brake disk every 18 months or so at Audi main dealer for a heap of cash, about £380.
Once while picking up some spark plugs at an independent auto spares shop based 5 minutes drive from this same Main dealer, a well know mechanic of their’s pulled up in a plain white van wearing audi overalls that were slightly obscured by his bomber jacket, and proceeded to “pick up” 10 packs of Audi A4 aftermarket Front Brake disk and a heap of after market pads.
These were the exact same items costing £49 for front disk and pads, that my dad had previously turned his nose up at when I suggested he buy them and save him self some cash having them fitted by an independent.
Sorry if this isn't really relevant but i just thought i'd mention it
Anyway, there are some parts that I will happily go after market with like brake disks, and others that I’d try and stick to OEM, like clutch! With regards to your qoutes if it says OEM on all three items here i'd go with the Cheapest, as it will / should be the exact same item in all 3 instance, differentiated only by packaging.