Sometimes, i really think that there's a lot of people who tend to think that those big name shops will have throat-cutting pricing, go ahead and get a quotation from them, not like they'll bite you for getting a quotation. You'll be surprised that the price difference between big name shops and no-name shops is very little in terms of installation charges, might as well pay slightly more for much better workmanship.

Alternatively, if you are around PJ area, i would also recommend Auto Seco in Sunway Mas Commercial area(near Aman Suria)

Well... for me, some reputable shops charge higher as they use specialised equipment when working on the install. Stuff like using routers to make perfect round holes instead of trying to get a round hole by using jigsaw then filing them down to make it round. All these are minor things most people didn't bother checking first.