There are 2 parts to your question;
1.Important for performance or...
2.Important for just riding?
1.Light stiff wheels will make a noticeable difference and a rigid frame
2.Definitely get the right saddle/seat post, cockpit and sort out your riding position to maximise your comfort.
That's a great distinction. I probably meant both in the same word. However since I already solved half of (1) by choosing a well-accepted frame that fit my budget, this becomes non-issue. For wheels, the Bike will come with Ksyrium Equippe and Conti 4000 tyres. I have to ride them first to see how I like it. But since the completed Canyon bike is so cheap I can sell the wheels without much concern for overall budget for the bike should I want to change them.
As for the Pedal issue, I have learnt from you guys and elsewhere that for decent manufactures, going up the price range is generally for lighter weight. Since this means a real money sink, I opt for a value, and dependable pedal (Shimano 105 SPD-SL). This should be more than good enough for me.
Thanks for all suggestion.