Upload & Sell: Off
I've ordered a Drobo 5D with thunderbolt and USB 3.0 access. It will give me speedy external storage for when my internal drives are too full to hold everything or just to hold the photos that I am less likely to want while my macbook pro is being used elsewhere as a portable. Most other external options will suffer from slow HDD speeds or slow interface speeds and will therefore slow down Lr.
So long as the external storage is on-line the work flow does not change because the one catalog still holds all of the photos. Also, the preview cache lets me see the external photos (but not edit them) even when they are off-line.
Just be sure to use Lr to relocate the files to other drives or folders or else the catalog will be compromised. The idea is to avoid splitting the photos into multiple catalogs because Lr searching can only be done to one catalog at a time, but know that a single catalog can cover multiple drives, whether on-line or off-line.
The time taken to cull photos is one reason why some people recommend that you don't do it - instead, spend the time on the good photos. Trouble is, the process of identifying the good photos takes just as long but you had to do it anyway.
I have recently started a new work flow that involves transferring the new photos to Lr via an auto-import folder on a speedy SSD, then doing the barest minimum image editing to allow me to judge how much I like the images as a first impression with little regard to image quality, and then applying a rating. Later I will apply a label that indicates how good or bad the images are and whether they are fixable or cannot be improved, etc. This takes more time than the rating process but because I have already used ratings to show which images I liked most I can use that to prioritize which ones I label first. Finally, I'll use the combination of rating and label to make smart collections that will instantly present the all-round best images, second best, etc. Other filters can narrow them down to relevant subjects, dates, gear, whatever.
Lr is based on a database and like all databases you get the best out of it only if you put the time and effort into feeding it with usable information. This means you should apply relevant ratings, labels, keywords and so on. In the short term this is certainly tedious but in the long term - once you catch up with your backlog of photos - Lr will become a far more friendly search tool that will seem more helpful than tedious.
Start with ratings and labels but first come up with a workable system - you only have five of each to play with. Then work on keywords. Start with simple, big-picture categories and refine them with more detailed info only if you need to. e.g. you could use "travel" as a broad category and rely on the image capture dates to find what you need, but if you need to pull out photos of a certain subject or trip then do so but also identify them with a new keyword and/or collection. The next time you need them they will be there instantly.