Originally posted by Moropo My wife is pregnant and I know I will be taking a lot of pictures, I assume most of them being indoors low lighting.
Congratulations, You will enjoy.
In terms of photography, you want a lens that is AF, fast (for low light) and will give you great IQ (no matter). Based upon a similar experience, I would recommend three lenses:
FA31mm f1.8 - Fast, great IQ, work extremely well indoor and outdoor
DA*55mm f1.4 - Fast, excellent IQ based upon many PF reviews (I do not have it)
FA77mm f1.8 - Superb, fast, the best Pentax lens in a recent PF vote, short tele
I would suggest that you use first your DA18-55 and see what focal length your wife and you favor: 30mm, 40 mm or 50-55mm. Then you can refine your choice. Persoanlly I love the FA77mm for portrait and it works well with family shots. That would be my recommendation No. 1. My second recommendation would be to buy it used from PF marketplace, keh.com or reputed dealers on the bay. There are excellent 2nd hand/used copies on the market and they are as good as the new ones IMHO.
Hope that the advice will help.