I can understand the business decision and the associated risk very well.... and I believe you immediately that you wish to have your games with voices. I just wanted to say that even though the persons voicing BH1 weren't professionals (as you said), I really really enjoyed BH1 BECAUSE of the full voices. Of course, as customers, we want long games with full voices at no cost, but, alas, there is no such thing as a free lunch.
Personally, I am willing to pay more to get voices, and even to sacrifice (ONLY A TINY BIT) of the game length to have voices added, but it is, of course, your responsibility to find the optimal decisions based on risk, cost, expected revenues and a number of other parameters.
Maybe you could help finding more funding by using a service like http://www.kickstarter.com/ to get a better financial basis for developing your games and/or for funding voice add-ons.
Anyway, I WILL buy BH2, once it is available...
