I also agree with Roger. For your 162 cm x 54 kg, a full-on 10 m2 racing sail will be quite heavy to handle. Such a big sail will be a real nightmare upon uphauling, especially when the wide luff is full of water.
Now, choosing a big sail depends on what wind range and what gear to use :
1) to match your Serenity quite nicely, I would suggest you to consider the Severne Raceboard 8.5 m2 sail. This sail is ultra-light, has only 3 cambers in a narrow luff pocket, rigs on a 490 cm mast. The big advantage is that you can fine tune the sail for non-planing conditions very efficiently : tight leech and a deep draft forward to get maximum power in light winds. Should the wind increase significantly, you can fine tune the sail for high wind : floppy leech and a flatter draft forward.
Another alternative would be a Raceboard 9.5 m2 sail, lighter and more powerfull in non-planing conditions than your Sailworks Retro 10 m2 that you got in 2007 (http://www.star-board.com/forum/showthread.php?t=1762
2) if you want a sail to match your Serenity in non-planing conditions + another wide planing board when wind is stronger, better consider an Overdrive 8.5 or 9.5 m2. Howerver, I fear that an Overdrive 9.5 m2 is quite big and heavy for your body IMHO and might weight more than your current Sailworks Retro 10 m2 (5.4 kg in 2007 according to specs: http://sailworks.com/previous/2007_S...#anchorretro05
3) if you want a wide planing board to be able to start and sustain the planing as early as possible (7-9 knots), I'm pretty sure you don't need a Formula + 10 m2 sail. For ultra-light weight rider like you, I've found that too wide a board doesn't bring any advantages in term of super early planing. Something 70-75 cm wide + 8.5-9.0 sail is plenty enough for example IMHO.
What are your gear other than the Serenity? Boards (still with Mistral Malibu and Flow?) and sail size (still 6.5/7.5/8.5/10 m2) and model (still Sailworks Retro) ?