Does this sound a reasonable budget for my upcoming newborn?

Car seat estimate seems high - you can do better with a Graco or last year's model, check Albeebaby and Amazon. Sometimes they go on sale for $90. You don't need Lamaze class - women have had babies for thousands of years without Lamaze. Take a class from the hospital instead, sometimes they are free or very cheap. You will likely need more clothes, but only basics like onesies and bodysuits until the baby is several months old. Diapers are going to cost alot more than $50. For bedding, all you need is a sheet and a few receiving blankets. Don't spend money on bumpers etc, theyre not recommended due to the risk of SIDS and are usually very overpriced. If you will breastfeed your cost of bottles goes way down too.