Have you searched at thrift stores, craigslist list and sewing- quilting groups? Since you are having the one machine serviced I would rethink buying an expensive machine.
As far as the repair time, the three weeks quoted could be on the shorter time, some repair shops have a longer waiting time and have call lists for machine repairs.
If you're in any kind of quilting group you might want to ask to see if anyone has a machine just sitting in their closet not being used and would love a new home where it could be used.
Do you just sew at home? Do you take your machine to quilting classes? The mechanical machines will tend to last longer as there are less electronics to get messed up. Are you wanting a machine to do embroideries? Is your sewing mostly what we use for quilting stitches? Does your machine or do you have a walking foot? Your sewing needs and style would greatly influence the decision of which machine would be best.
With all of that said there are a lot of quilters who at classes bring their old Singer featherweights or they bring the newer Janome Gem..and there are several versions. Most like the Platinum as it has all the bells and whistles and is a smaller lighter 3/4 machine.
Good luck in your search for an additional machine.
Pam M