$$$ to spend depends on how busy you plan to keep
I suspect that most of the guys advising you to spend more money on new equipment are into tree care pretty hard and heavy. I'm sure that the advice they give is well-intended based upon their workloads and experience with new and used equipment.
I would, however, advise you to first look at your own workload and come up with some figures for how many hours per month you estimate you can use a bucket truck. Do the same for a chipper/chip truck. Then do it for a forestry bucket/chipper package.
Those figures will tell you your time/cost savings by implementing the new equipment. If your greatest savings will be in being able to chip brush rather than haul it, then follow the advice given in this forum and spend more money on a quality chipper. (I don't use a winch but I do have a mini skidsteer to haul debris). This may be another option to consider - especially if you have large logs to haul also.
If your greatest cost savings wil be in using a bucket truck, then invest your money in that direction and continue to haul brush for awhile longer. Personally, I believe you can buy both a good used bucket truck (55' overcenter boom) and a good used chipper (12" disk) for the $50k you have budgeted - $30-35k for the truck and 15-20k for the chipper. Make sure both are inspected by a reputable service company before you buy - it'll be worth the money to know what you're buying.
Another consideration for the truck is whether you're working in a small local area or doing a lot of over-the-road work. Obviously, the latter will require a truck in a little better running condition if you're going to put a lot of miles on the truck. Although I've now scaled down a bit and am part-time, my last truck was a 1995 F800 utility with a 55' Altec A600 boom. The truck worked great even though the boom wasn't overcenter (get overcenter). I had both the truck and boom inspected before I bought them so I knew I had a few repairs to make. I paid around $15,000 for the truck and put about $6000 into boom and engine repairs. I painted it myself at a cost of under $500. For about $21,500, I had a very reliable truck and sold it after using it for a few years for $1000 more than I put into it.
As for a chipper, I made a mistake and bought a used lemon sight unseen from Harv's Sales in Michingan (see post in the Equipment Forum about problems with this dealer). With a little care and a pre-purchase inspection, I'm confident you can get a good used 12" chipper for $15-20k. Just don't buy anything sight unseen or from photos. As I found out, photos can hide a lot of mechanical problems!
You'll be amazed at how much time a 12" chipper can save you. Sure a bigger capacity can be nice at times but, it also means more expense up front and higher repair costs. You'll spend more money at a big dealership but probably get equipment that has truly been checked out so, you'll know what you're buying. I wouldn't be afraid to buy from a private party or a small dealer but, either take a mechanic along with you or ask to take the equipment for a day or two so you can have it checked out by a local service shop. The few hundred dollars you spend on havign the equipment checked out by someone who knows what to look for may save you thousands in the long haul...
I presume you've checked out the Tree Equipment Trader magazine or website?
Good luck!