It is unfortunate that heated stirrers are so expensive. You can sometimes find some fairly decent units on eBay however, though I rarely see anything under 180USD worth buying.
Another rule of thumb in cases such as these is to choose a unit with a min. of 500 watts or more of heating power. Otherwise, you risk not having the capacity to heat a pot of CS, as many manufacturers amplify their specs.
Having said that, one of the vital aspects of using a stirrer is where it will dissipate the particulate away from the anode and discourage agglomeration. In contrast to air which not only little in terms of distribution, but will also contribute to the introduction of oxygen in the solution, which in turn, promotes the production of silver oxides.
Whereas a heated stirrer on the other hand, will combat this by lowering the oxygen in the solution(moving free oxygen out) as well as inducing a reduction at the cathode from hydroxide, back into metallic silver. Which can be observed by the absence of the black residue (oxides) at the cathode in exchange for a metallic silver residue.
There are of course other benefits to using a heated stirrer, though these would be the main advantages imo.
PS. you can sometimes come across a none heated stirrer for a fairly decent price(under 100). Which can also prove helpful in increasing the quality of your solution, though the benefits will likely remain limited to that of dispersion.
As for Ionic Solutions I'm thinking the challenges are due to the nature of the solutions. ie, it would be difficult if not impossible to make a stable ionic solution in that they are; 1) under the solubility limit(low) and 2) prone to oxidation and/or destabilization. - my two cents
That said, it is possible however, to make a high-quality ionic solutions with the help of a heated stirrer and some nifty process methods.