What do you feel about philips Avent bottles? I wanted to buy more nipples for my 2 month old because he's in medium flow now and the slow newborn flow is not working anymore.he also drinks rice cereal so the slow flow does not work but the bottles are smaller 4oz and I think it would be smarter to just buy bigger bottles with medium flow nipples so he can grow into them??? I have medela bottles I just opened that are medium flow hopes it works...opinions?