With a new start into astronomy observing for $4000 budget - it's OK - but for astrophorgraphy, that's a bit thin - the best money you can spend is for the equatorial mount with/without GoTo since you're intending to have an obs - next then is the OTA
Of course 12" aperture is good - but it has its foibles - you'll find that you need to spend at least $10-$12K for a good mount (others of course have done it with cheaper mounts but you have to take time/frustrations into the equation when it comes to "overloading" a cheapie mount)
I've found over a period of time that you will need several OTAs to image different stellar bodies/objects etc and the best way to come to a decision as to which OTA to get first is to attend a star-party hosted by one of the clubs near you and have a feel for what's right for your needs and start off with a combination that suits your budget and one that you'll use always
Be prepared - it's a deeeeeeeep money pit as far as astro-imaging is concerned
HTH
Cheers
Bill