I purchased the following accessories for my 2007 HCH-II:
- Trunk liner
- All weather floor mats
- Cup holder inserts (for rear doors)
I recommend all of these accessories.
The trunk liner protects the trunk floor from any dirt or spills and adds a nice finished look. If the trunk is empty, it is easy to lift up or remove the liner to access the spare tire and tire changing tools.
The all weather floor mats are the best mats I have ever installed in any of my cars. The fit is perfect. Mine are black rubber, custom fitted to the 06-07 Civic floor space. Dirt or liquids cannot reach the carpet. These mats are easy to remove and clean to keep in new condition. These mats are also available in beige color. Others in this forum have commented that their beige mats show scuffs and stains. I strongly recommend these mats in black.
The cup holder inserts for the rear doors hold 12 oz soda cans or the typical containers for bottled water up to 20 oz. The "Big Gulp" sized containers like you get a a fast food drive through will not fit into these holders. The asking price for this accessory is fairly high for what you get (two pieces or rubbery plastic inserts). Nevertheless it is nice to add two extra cup holders for the back seat area for those occasions when you need a place to store a couple of additional beverages. It takes 1 second to install or to remove these cup holders.
I have no experience with the roof racks or other HCH accessories.
Hope you find this helpful