I did quite a bit of research on the web about Jon Reau wigs awhile back and I'll share what I found. I see the one you're looking at is a synthetic. Synthetic wigs are what big labels like Renau do best because the hair quality can be easily maintained in manufacturing. Reviews of Renau's human hair wigs tend to be very spotty. Sometimes the hair quality is OK and other times its very poor. Renau is well known for their cap quality, though.
Two things would prevent me from buying the Top Secret 12", though. One is that it doesn't have a lace front. With non-banged styles like that you really want a lace front. Renau has a nifty no-adhesive lace front system with some of their wigs and it's probably worth the extra money.
The other thing, for me, though, is that it's synthetic. After wearing both synthetic and HH wigs over the years, I've decided human hair is really the only way to go for a real hair look and for wig longevity. The drawback is they require a lot of care and styling to keep them looking good.
As for color, I really like Renau's FS26/31 mix, too. It's a beige-to-blonde highlight mix that has an oddly pale overall tone when seen as a full wig, but it's not bad. The downside is that I wouldn't recommend it for a synthetic. The most convincing synthetics tend to be the darker shades. Blonde synthetic wigs seem to usually look plasticy, I think. There may be treatments that can dull the gloss a bit, but I've not tried it.
As for your age, I see more and more women over 50 going blonde and it often seems to do wonders for making them seem younger and fresher. Go for it. But consider human hair if you do. I think the best human hair wigs come from smaller independent sources. One I've heard very good reviews of is Model Lace Wigs in Las Vegas, but check around the web. There are many fine smaller wig dealers with great wigs and at lower prices than the big labels. I'll warn you, though, that I rarely hear of a wig shopper who finds the perfect wig the first try. Most wig buyers end up buying a few of them before they have one they are satisfied with.