I would ask yourself,do you use the hrw in the soft-top?If yes,then you are going to miss it on a hard top if it does not have one fitted.

To be honest, I'd wait and get one with the HRW - far better when you come to sell. When I had my MX5, the rear window did steam up until I switched the HRW on.

Check ebay as a source and MX5 forums. Best to get one that matches the car, and be patient - took me 6 months to find the right one. Not worth skimping on.

Another point, make sure if you get one with the HRW it has the curly electric lead. Behind the passenger seat under the parcel shelf matting there is a split, and under you will find the cable for the soft top HRW. Unplug and plug in new one - it can be fiddly as it's best done with roof on to avoid damaging HRW terminals - may need a connector tab pressing with a screwdriver.

After my first fitting, there was wind noise from windscreen rail, so it needed minor adjustment of the fine adjuster on the catches. There are two for windscreen as per soft top, and one catch each behind each seat near the seat belt run. Check you have the brackets behind the seats on the car and dont need to buy them - oh, and that you have the stubby chrome spigots on the back - also known as 'frankenstein bolts'.

More here: www.mx5nutz.com/forum/index.php?showtopic=137650 and a general Google brings up plenty of info.

Two final tips - when fitting, best use 2 people (one each side - avoids expensive damage from dropping), and make sure after sliding over spigots first, the top is fully pushed forwards before trying to fit any other clips.