Pick up a used 497 Autostar. Sell the 494 on ebay for $35 and pay $70-80 for a 497. The 506 is hard to find and overpriced when you do. The 497 has the MAX232 chip on board so a simple to make of find 505 cable is all you will need. This gives you the benefits of the 497 which has had several updates to the firmware, while the 494 never got beyond ver 1.0. You will also have access to a much larger database of objects and third party firmware patches the give the 497 even greater utility.
In hindsight the 494 was a mistake. Sure at the time building a controller with less memory and no serial interface may have made sense, but as the cost of components dropped and that of maintaining two production lines went up this became clearer. Additionally, the AutoStar system became very successful and the production volume has brought the cost of the electronics to a small part of a mount's cost. Of course, I'm still trying to understand the rational for the Autostar II and III. Yes, the electronics in the LX200GPS and LS are more complex, but Celestron has similar models that use the same hand controller throughout the product line. And don't even ask about my LX80 doorstop.
If you don't have RS232 port on your PC you will need to get from DE9 to USB. You don't need to spend $50 on the Meade converter, just be sure to get a Keyspan from a US vendor. This one is $12, eBay item number: 231245664512. Don't settle for a USB converter that advertises a FTDI microchip as there are now counterfeit FTDI chips flooding the market. Ain't China wonderful.
Look at it this way: Inside even your humble 494 is the same processor that powered the original 1980 Mac. The firmware gives it a map of the sky to search for objects whose celestial coordinates are in its database or coordinates you input. The planetarium software running on the PC, tablet, etc. is also a sky map. When you select an object on the screen the program converts the screen's pixel location to celestial coordinates and transmits them to the telescope.