It's always surprising how much better 900MHz and 433Mhz is in a residential area (walls and floors). So this is just a CC1101 module. How much did you pay for these? If you check e-bay, there are usually CC1101 modules available. I was going to try a CC1101 solution about a year ago, but supply for a lot of TI stuff including the CC1101 dried up for a long time. If you want to roll your own, they have already tuned one chip baluns for the CC1101 on Digikey. Makes it real easy.
I have the RF2500 as one of the transceivers I was testing and ya, they are generally well known for their poor antenna design. They hardly worked throughout my house.
I hang onto my old 900Mhz Panasonic cordless phone, because the range is so much better than the 2.4Ghz I've tried.